Imaging apparatus and imaging method, camera module, and electronic apparatus capable of detecting a failure in a structure in which substrates are stacked

ABSTRACT

The present disclosure relates to an imaging apparatus and an imaging method, a camera module, and an electronic apparatus that are capable of detecting a failure in an imaging device having a structure in which a plurality of substrates are stacked. 
     The timing at which a row drive unit provided in a second substrate outputs a control signal for controlling accumulation and reading of pixel signals in a pixel array provided in a first substrate is compared with the timing at which the control signal output from the row drive unit is detected after passing through the pixel array. Depending on whether or not the timings coincides with each other, a failure is detected. The present disclosure can be applied to an imaging apparatus mounted on a vehicle.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit under 35 U.S.C. § 120 as acontinuation application of U.S. application Ser. No. 16/302,906, filedon Nov. 19, 2018, now U.S. Pat. No. 10,659,707, which claims the benefitunder 35 U.S.C. § 371 as a U.S. National Stage Entry of InternationalApplication No. PCT/JP2017/020369, filed in the Japanese Patent Officeas a Receiving Office on May 31, 2017, which claims priority to JapanesePatent Application Number JP2016-109196, filed in the Japanese PatentOffice on May 31, 2016, each of which applications is herebyincorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to an imaging apparatus and an imagingmethod, a camera module, and an electronic apparatus, and moreparticularly, to an imaging apparatus and an imaging method, a cameramodule, and an electronic apparatus that are capable of detecting afailure in a device having a structure in which a plurality ofsubstrates are stacked.

BACKGROUND ART

Imaging devices that capture images have become smaller in size, and arenow being used for various purposes.

In recent years, vehicles with driving support functions have becomecommon. With the driving support functions, a scenery in front of thevehicle is captured, and the lane on which the vehicle is running, thevehicle running in front of the vehicle, a pedestrian rushing toward thelane, and the like are recognized in accordance with the captured image.Danger can be avoided in this manner.

In an imaging device as one of such functions, however, erroneousdetection is performed when there is a failure. As a result, appropriatedriving support cannot be provided. Therefore, there is a possibilitythat danger might not be avoided with the driving support.

For this reason, an imaging device for vehicles is required to have afunction to detect a failure during operation of an analog circuit,according to ISO 26262 (an international standard for functional safetyof electrical and/or electronic systems in production automobiles).

While there is such a requirement, a technique for detecting a failurerelated to disconnection of a horizontal signal line in an imagingdevice has been suggested (see Patent Documents 1 and 2).

CITATION LIST Patent Document

Patent Document 1: Japanese Patent Application Laid-Open No. 2009-118427

Patent Document 2: Japanese Patent Application Laid-Open No. 2009-284470

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

Meanwhile, in the imaging apparatuses that have become common in recentyears, a first substrate including photodiodes that generate pixelsignals corresponding to the amounts of incident light, and a secondsubstrate including a signal processing unit or the like that performssignal processing on the pixel signals generated by the photodiodes arestacked, and are electrically connected.

With the above mentioned technique for detecting a failure, however, itis not possible to detect a failure in an imaging apparatus having astructure in which a plurality of substrates are stacked.

The present disclosure is made in view of such circumstances, andparticularly, aims to enable detection of failures in an imagingapparatus having a structure in which a plurality of substrates arestacked.

Solutions to Problems

An imaging apparatus according to a first aspect of the presentdisclosure is an imaging apparatus that includes: a first substrateincluding a pixel and a pixel control line; and a second substrate, thefirst substrate and the second substrate being stacked on each other. Inthe imaging apparatus, the second substrate includes a row drive unitand a failure detector. One end of the pixel control line is connectedto the row drive unit via a first connection electrode, and the otherend of the pixel control line is connected to the failure detector via asecond connection electrode. The row drive unit supplies a controlsignal for controlling operation of the pixel to the pixel control linevia the first connection electrode. The failure detector detects afailure in accordance with the control signal supplied via the firstconnection electrode, the pixel control line, and the second connectionelectrode.

The first connection electrode and the second connection electrode maybe formed with through electrodes penetrating through the firstsubstrate and the second substrate, and the first substrate and thesecond substrate may be stacked and be electrically connected by thethrough electrodes.

The pixels may be arranged in an array. The imaging apparatus mayfurther include a control unit that outputs address information about acurrent target among the pixels and information about timing at whichthe pixel specified by the address information is controlled. Thefailure detector may include: a row drive unit that supplies a controlsignal for controlling operation of the pixel, the row drive unit beingspecified by the address information output from the control unit; adetector that detects the control signal for controlling operation ofthe pixel and outputs a detection signal, the control signal beingsupplied from the row drive unit specified by the address informationoutput from the control unit; and a pulse output failure detector thatdetects a failure in a pulse output of the control signal, depending onwhether or not the detection signal is output when the control signalfor controlling operation of the pixel specified by the addressinformation output from the control unit is detected by the detector atthe timing at which the pixel specified by the address information iscontrolled.

The detector may include a switching gate that detects the controlsignal for controlling operation of the pixel, the switching gate beingspecified by the address information output from the control unit, andthe detector may supply electric power only to the switching gatespecified by the address information output from the control unit. Whenhaving detected the control signal for controlling operation of thepixel, the switching gate may output a Hi signal to a bus set for eachcorresponding control signal. The pulse output failure detector mayinclude a plurality of holding units that hold a value for each controlsignal, the value depending on a signal output to the bus set for eachcontrol signal and a signal indicating the timing at which the pixelspecified by the address information is controlled, and detects afailure in a pulse output of the control signal, in accordance with thevalue held by the holding units.

The plurality of holding units may hold a value for each control signal,the value depending on a signal output to the bus set for each controlsignal and a fixed signal indicating that the pixel specified by theaddress information is in a controlled state. The pulse output failuredetector may detect a failure in a pulse output of the control signal,in accordance with the value held by the holding units.

The row drive unit and the first substrate may be connected by the firstconnection electrode formed with a through electrode, and the detectorand the first substrate may be electrically connected by the secondconnection electrode formed with another through electrode differentfrom the through electrode.

The control unit may output the address information about the currenttarget among the pixels to the row drive unit and the detector. The rowdrive unit may output selection information about an address of the rowdrive unit, the selection information corresponding to the addressinformation. The detector may output selection information about anaddress of the detector, the selection information corresponding to theaddress information. The failure detector may include an address selectfunction failure detector that compares the selection information aboutthe address of the row drive unit and the selection information aboutthe address of the detector with the address information output from thecontrol unit, and, in accordance with a result of the comparison,detects a failure in an address select function in the row drive unitand the detector.

An imaging method according to the first aspect of the presentdisclosure is an imaging method implemented in an imaging apparatusincluding: a first substrate including a pixel and a pixel control line;and a second substrate, the first substrate and the second substratebeing stacked on each other. The second substrate includes a row driveunit and a failure detector. One end of the pixel control line beingconnected to the row drive unit via a first connection electrode, andthe other end of the pixel control line being connected to the failuredetector via a second connection electrode. The imaging method includesthe steps of: the row drive unit supplying a control signal forcontrolling operation of the pixel to the pixel control line via thefirst connection electrode; and the failure detector detecting a failurein accordance with the control signal supplied via the first connectionelectrode, the pixel control line, and the second connection electrode.

A camera module according to the first aspect of the present disclosureis a camera module that includes: a first substrate including a pixeland a pixel control line; and a second substrate, the first substrateand the second substrate being stacked on each other. In the cameramodule, the second substrate includes a row drive unit and a failuredetector. One end of the pixel control line is connected to the rowdrive unit via a first connection electrode, and the other end of thepixel control line is connected to the failure detector via a secondconnection electrode. The row drive unit supplies a control signal forcontrolling operation of the pixel to the pixel control line via thefirst connection electrode. The failure detector detects a failure inaccordance with the control signal supplied via the first connectionelectrode, the pixel control line, and the second connection electrode.

An electronic apparatus according to the first aspect of the presentdisclosure is an electronic apparatus that includes: a first substrateincluding a pixel and a pixel control line; and a second substrate, thefirst substrate and the second substrate being stacked on each other. Inthe electronic apparatus, the second substrate includes a row drive unitand a failure detector. One end of the pixel control line is connectedto the row drive unit via a first connection electrode, and the otherend of the pixel control line is connected to the failure detector via asecond connection electrode. The row drive unit supplies a controlsignal for controlling operation of the pixel to the pixel control linevia the first connection electrode. The failure detector detects afailure in accordance with the control signal supplied via the firstconnection electrode, the pixel control line, and the second connectionelectrode.

According to the first aspect of the present disclosure, a firstsubstrate including a pixel and a pixel control line, and a secondsubstrate including a row drive unit and a failure detector are stackedon each other. One end of the pixel control line is connected to the rowdrive unit via a first connection electrode, and the other end of thepixel control line is connected to the failure detector via a secondconnection electrode. The row drive unit supplies a control signal forcontrolling operation of the pixel to the pixel control line via thefirst connection electrode, and the failure detector detects a failurein accordance with the control signal supplied via the first connectionelectrode, the pixel control line, and the second connection electrode.

An imaging apparatus according to a second aspect of the presentdisclosure is an imaging apparatus that includes: a first substrateincluding a pixel and a vertical signal line connected to the pixel; anda second substrate, the first substrate and the second substrate beingstacked on each other. In the imaging apparatus, the second substrateincludes a signal supply circuit, an analog-to-digital conversioncircuit, and a failure detector. One end of the vertical signal line isconnected to the signal supply circuit via a first connection electrode,and the other end of the vertical signal line is connected to theanalog-to-digital conversion circuit via a second connection electrode.The signal supply circuit supplies a dummy pixel signal to the verticalsignal line via the first connection electrode. The analog-to-digitalconversion circuit outputs a digital signal in accordance with the dummypixel signal. The failure detector detects a failure in accordance withthe digital signal.

According to the second aspect of the present disclosure, a firstsubstrate including a pixel and a vertical signal line connected to thepixel, and a second substrate and the first substrate are stacked oneach other. The second substrate includes a signal supply circuit, ananalog-to-digital conversion circuit, and a failure detector. One end ofthe vertical signal line is connected to the signal supply circuit via afirst connection electrode, and the other end of the vertical signalline is connected to the analog-to-digital conversion circuit via asecond connection electrode. The signal supply circuit supplies a dummypixel signal to the vertical signal line via the first connectionelectrode. The analog-to-digital conversion circuit outputs a digitalsignal in accordance with the dummy pixel signal, and the failuredetector detects a failure in accordance with the digital signal.

An imaging apparatus according to a third aspect of the presentdisclosure is an imaging apparatus that includes: a first substrate onwhich a pixel is mounted; and a second substrate on which a signalprocessing unit that performs signal processing on an image captured bythe pixel is mounted. The first substrate and the second substrate arestacked and are electrically connected, and the signal processing unitdetects a failure through the signal processing.

According to the third aspect of the present disclosure, a firstsubstrate on which a pixel is mounted, and a second substrate on which asignal processing unit that performs signal processing on an imagecaptured by the pixel is mounted are stacked on each other and areelectrically connected, and the signal processing unit detects a failurethrough the signal processing.

Effects of the Invention

According to the present disclosure, it is possible to detect a failurein an imaging device having a structure in which a plurality ofsubstrates are stacked.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram for explaining an example configuration of a vehicleaccording to the present disclosure.

FIG. 2 is a diagram for explaining an example configuration of the frontcamera module shown in FIG. 1.

FIG. 3 is a flowchart for explaining a driving support process to beperformed by the vehicle shown in FIG. 1.

FIG. 4 is a diagram for explaining an example configuration of thehardware that forms the imaging device and the front camera ECU shown inFIG. 2.

FIG. 5 is a diagram for explaining an example configuration of a firstembodiment of the functions that form the imaging device and the frontcamera ECU shown in FIG. 2.

FIG. 6 is a diagram for explaining a failure detection process to beperformed by the imaging device and the front camera ECU shown in FIG.4.

FIG. 7 is a flowchart for explaining a row address selecting functionfailure detection process to be performed by the imaging device and thefront camera ECU shown in FIG. 4.

FIG. 8 is a diagram for explaining a row address selecting functionfailure detection process to be performed by the imaging device and thefront camera ECU shown in FIG. 4.

FIG. 9 is a diagram for explaining an example configuration of thecontrol line gate shown in FIG. 4.

FIG. 10 is a diagram for explaining an example configuration of thepulse output failure detector shown in FIG. 4.

FIG. 11 is a flowchart for explaining a control line gate managementprocess to be performed by the control line gate shown in FIG. 4.

FIG. 12 is a flowchart for explaining a pulse output failure detectionprocess to be performed by the pulse output failure detector shown inFIG. 4.

FIG. 13 is a diagram for explaining a pulse output failure detectionprocess to be performed by the pulse output failure detector shown inFIG. 4.

FIG. 14 is a diagram for explaining a modification of the pulse outputfailure detector as a first modification of the functions that form thefirst embodiment.

FIG. 15 is a diagram for explaining a pulse output failure detectionprocess to be performed by the pulse output failure detector shown inFIG. 14.

FIG. 16 is a diagram for explaining a modification of the imaging deviceand the front camera ECU as a second modification of the functions thatform the first embodiment.

FIG. 17 is a flowchart for explaining a pixel control line failuredetection process to be performed by the imaging device and the frontcamera ECU shown in FIG. 16.

FIG. 18 is a diagram for explaining an example configuration of a secondembodiment of the imaging device and the front camera ECU shown in FIG.2.

FIG. 19 is a diagram for explaining an ADC+TCV failure detection processto be performed by the imaging device and the front camera ECU shown inFIG. 18.

FIG. 20 is a diagram for explaining a first operation test in theADC+TCV failure detection process to be performed by the imaging deviceand the front camera ECU shown in FIG. 18.

FIG. 21 is a diagram for explaining a second operation test in theADC+TCV failure detection process to be performed by the imaging deviceand the front camera ECU shown in FIG. 18.

FIG. 22 is a diagram for explaining a third operation test in theADC+TCV failure detection process to be performed by the imaging deviceand the front camera ECU shown in FIG. 18.

FIG. 23 is a diagram for explaining a fourth operation test in theADC+TCV failure detection process to be performed by the imaging deviceand the front camera ECU shown in FIG. 18.

FIG. 24 is a flowchart for explaining an ADC+TCV failure detectionprocess to be performed by the imaging device and the front camera ECUshown in FIG. 19.

FIG. 25 is a diagram for explaining a first modification of thefunctions that form the second embodiment.

FIG. 26 is a diagram for explaining an example configuration of thefunctions that form a third embodiment.

FIG. 27 is a diagram for explaining an example configuration of thecorrection unit shown in FIG. 26.

FIG. 28 is a diagram for explaining a method of correcting pixel signalson a row-by-row basis and a column-by-column basis.

FIG. 29 is a flowchart for explaining a correction process to beperformed by the correction unit shown in FIG. 27.

FIG. 30 is a flowchart for explaining a correction process to beperformed by the correction unit shown in FIG. 27.

FIG. 31 is a diagram for explaining an example configuration for forminga fourth embodiment.

FIG. 32 is a diagram for explaining a first example configuration inwhich three chips are stacked to form a fifth embodiment.

FIG. 33 is a diagram for explaining a second example configuration inwhich three chips are stacked to form the fifth embodiment.

FIG. 34 is a diagram for explaining a third example configuration inwhich three chips are stacked to form the fifth embodiment.

FIG. 35 is a diagram for explaining a fourth example configuration inwhich three chips are stacked to form the fifth embodiment.

FIG. 36 is a diagram for explaining a fifth example configuration inwhich three chips are stacked to form the fifth embodiment.

FIG. 37 is a diagram for explaining an example configuration of pixelsignal TSVs in a case where comparators and counters are disposed in thesame chip.

FIG. 38 is a diagram for explaining an example configuration of pixelsignal TSVs in a case where comparators and counters are disposed indifferent chips.

FIG. 39 is a diagram for explaining an example configuration of a columnADC.

FIG. 40 is a diagram for explaining an example configuration of an areaADC.

FIG. 41 is a diagram for explaining a schematic example structure in acase where an imaging device having a two-layer structure is formed witha WCSP.

FIG. 42 is a diagram for explaining an example circuit layoutconfiguration of the imaging device shown in FIG. 41.

FIG. 43 is a diagram for explaining an example cross-section structureof the imaging device shown in FIG. 41.

FIG. 44 is a diagram for explaining an example circuit layout in a casewhere a different upper-lower wiring line connection structure of theimaging device in FIG. 41 is used.

FIG. 45 is a diagram for explaining the structure of the imaging devicein FIG. 41 in detail.

FIG. 46 is a diagram for explaining a first modification of the imagingdevice shown in FIG. 41.

FIG. 47 is a diagram for explaining a second modification of the imagingdevice shown in FIG. 41.

FIG. 48 is a diagram for explaining a third modification of the imagingdevice shown in FIG. 41.

FIG. 49 is a diagram for explaining a schematic example structure in acase where an imaging device having a three-layer structure is formedwith a WCSP.

FIG. 50 is a diagram for explaining a schematic example structure in acase where an imaging device having a three-layer structure is formedwith a WCSP.

FIG. 51 is a block diagram showing an example configuration of animaging apparatus as an electronic apparatus in which a front cameramodule according to the present disclosure is used.

FIG. 52 is a diagram for explaining examples of use of a front cameramodule to which the technique of the present disclosure is applied.

FIG. 53 is a block diagram schematically showing an exampleconfiguration of a vehicle control system.

FIG. 54 is an explanatory diagram showing an example of the installationpositions of imaging units.

MODES FOR CARRYING OUT THE INVENTION

The following is a detailed description of preferred embodiments of thepresent disclosure, with reference to the accompanying drawings. Itshould be noted that, in this specification and the drawings, componentshaving substantially the same functional configurations are denoted bythe same reference numerals, and explanation of them will not berepeated.

In addition, in the description below, explanation will be made in thefollowing order.

1. First embodiment

2. Second embodiment

3. Third embodiment

4. Fourth embodiment

5. Fifth embodiment

6. Pixel signal TSVs

7. Types of ADCs

8. Example structure of WCSP

9. Example application to an electronic apparatus

10. Examples of use of an imaging device

11. Example applications to moving objects

1. First Embodiment

<Example Configuration of a Vehicle of the Present Disclosure>

Referring to FIG. 1, an example configuration of a vehicle according tothe present disclosure is described.

A vehicle 11 according to the present disclosure includes an ECU 31, afront camera module 32, a steering wheel 33, a headlamp 34, a motor 35,an engine 36, a brake 37, and a display unit 38.

The electronic control unit (ECU) 31 controls the overall operation ofthe vehicle 11 relating to electronic control. For example, the ECU 31performs operations relating to driving of various kinds and assists thedriver in driving, in accordance with information supplied from thefront camera module 32, the steering wheel 33, the headlamp 34, themotor 35, the engine 36, the brake 37, and the display unit 38.

The front camera module 32 includes an imaging device, and captures animage of the scenery in front of the vehicle 11, or more particularly,the scenery in front of the vehicle 11 that is running. In accordancewith the captured image, the front camera module 32 recognizes the laneon which the vehicle 11 is currently running, the vehicle running ahead,the pedestrians, and the like, and supplies the recognition results tothe ECU 31. The front camera module 32 also detects a failure or thelike of the built-in imaging device. In a case where a failure isdetected, the front camera module 32 notifies the ECU 31 to that effect.Through this process, the ECU 31 stops the operation relating to thedriving and the driving support using the recognition results based onthe image captured by the front camera module 32, and also causes thedisplay unit 38 to display a message to that effect.

The steering wheel 33 is designed for controlling the running direction,and is normally operated by the driver, which is a user. In some cases,however, the steering wheel 33 is controlled by the ECU 31.Specifically, in a case where a pedestrian or a vehicle is detected infront of the running vehicle by the front camera module 32, and there isa possibility of a collision, for example, driving support is providedso that the steering wheel 33 is controlled through a determination madeby the ECU 31, and a collision is avoided.

The headlamp 34 is a headlamp that illuminates the space in front of thevehicle 11, particularly in a situation where it is difficult for thedriver to see with his/her own eyes during nighttime or the like. Aswitch or the like (not shown) is usually operated by the driver, tocontrol switching on and off of the low beam and the high beam. Theheadlamp 34 is also controlled by the ECU 31 in some cases. For example,the following driving support is realized. In a case where an oncomingvehicle is detected by the front camera module 32, the ECU 31 determinesto switch the lighting from the high beam to the low beam. In a casewhere any oncoming vehicle is no longer detected, control is performedto switch the lighting back to the high beam.

The motor 35 and the engine 36 are power sources for driving the vehicle11. The motor 35 is driven by electric power, and the engine 36 isdriven by fuel such as gasoline or light oil. The motor 35 and theengine 36 are also controlled by the ECU 31. Specifically, in asituation where the efficiency with the engine 36 is poor, and the fuelefficiency is lowered, like at the start of running, for example, onlythe motor 35 is driven. Also, at a time when the efficiency with theengine 36 is high, for example, control is performed so that the drivingof the motor 35 is stopped, and the engine 36 is driven, depending onthe running condition. Further, in a case where a running vehicle or apedestrian is detected in front of the vehicle by the front cameramodule 32, driving support is provided so that the operation of themotor 35 and the engine 36 is stopped to assist in avoiding a crisis.

The brake 37 is operated by the driver to stop the running vehicle 11.Thus, the vehicle 11 is stopped. In some cases, the brake 37 is alsocontrolled by the ECU 31. Specifically, in a case where a runningvehicle or a pedestrian in front of the vehicle 11 is detected by thefront camera module 32, and emergency avoidance is necessary, forexample, driving support is provided so that the brake 37 to be operatedthrough a determination made by the ECU 31, and an emergency stop ismade.

The display unit 38 is formed with a liquid crystal display (LCD) or thelike. In cooperation with a global positioning system (GPS) device (notshown), for example, the display unit 38 achieves a navigation functionfor displaying information such as route guidance to a destination.Also, the display unit 38 is formed with a touch panel or the like, andalso functions as an operation input unit. Furthermore, in a case wherethe steering wheel 33, the motor 35, the engine 36, the brake 37, andthe like are operated to take an emergency avoidance action inaccordance with an image captured by the front camera module 32, forexample, the display unit 38 displays a message to that effect. When afailure of the front camera module 32 is detected, and the drivingsupport based on the captured image is stopped, the display unit 38 alsodisplays information indicating that the driving support is stopped.

<Example Configuration of the Front Camera Module>

Referring now to FIG. 2, an example configuration of the front cameramodule 32 is described.

The front camera module 32 is connected via a bus 51 similarly to theECU 31, the steering wheel 33, the headlamp 34, the motor 35, the engine36, the brake 37, and the display unit 38, so that these components canexchange data and signals with one another.

Further, the front camera module 32 includes a lens 71, an imagingdevice 72, a front camera ECU 73, and a module control unit (MCU) 74.

The lens 71 gathers incident light from the imaging direction in frontof the vehicle 11, and forms an image of the object on the imagingsurface of the imaging device 72.

The imaging device 72 is formed with a complementary metal oxidesemiconductor (CMOS) image sensor or the like. The imaging device 72captures an image formed by the lens 71 gathering light and forming animage of the object in front of the vehicle 11, and supplies thecaptured image to the front camera ECU 73.

In accordance with the image of the object in front of the vehicle 11captured by the imaging device 72, the front camera electronic controlunit (ECU) 73 performs image processing, an image analysis process, andthe like, such as lane detection, pedestrian detection, vehicledetection, headlamp detection, a signal recognition process, and imagecontrol, for example. The front camera ECU 73 supplies the results ofthe processes to the MCU 74. In addition to these processes, the frontcamera ECU 73 also detects a failure of the imaging device 72. In a casewhere a failure is detected, the front camera ECU 73 stops theoutputting of the results of the processes, and outputs informationindicating that a failure has been detected.

The MCU 74 converts the image processing results into information thatcan be recognized by the ECU 31 and the like, and outputs the resultantinformation to the ECU 31. Note that, in a case where informationindicating that a failure of the imaging device 72 has been detected isoutput from the front camera ECU 73 at this stage, the MCU 74 suppliesthe corresponding information to the ECU 31. In such a case, the ECU 31stops the driving support using the image processing results suppliedfrom the front camera module 32, and causes the display unit 38 or thelike to display information indicating that the driving support usingthe image processing results is stopped due to a failure of the imagingdevice 72. In this manner, the driver is made to recognize that thedriving support is not being provided.

<Driving Support Process>

Referring now to the flowchart in FIG. 3, a driving support process tobe performed by the vehicle 11 is described.

In step S11, the front camera ECU 73 determines whether or not thedisplay unit 38 is formed as a touch panel, and a driving support startinstruction has been issued by operating the touch panel, for example.The front camera ECU 73 repeats a similar process, until a drivingsupport start instruction is issued. Then, if a driving support startinstruction has been issued in step S11, the process moves on to stepS12, and a driving support process is started.

In step S12, the front camera ECU 73 performs a failure detectionprocess on the front camera module 32. The failure detection processhere may be the later described row address selecting function failuredetection process (FIG. 7), the pulse output failure detection process(FIG. 12 or 15), the pixel control line failure detection process (FIG.17), the ADC+TCV failure detection process (FIG. 24), or some otherfailure detection process, for example. The failure detection process inthis example may be performed during imaging, or may be performed whenthe driving support system is activated by turning on the vehicle powersupply, when the vehicle is subjected to pre-shipment inspection, orwhen defective products are eliminated at the factory.

In step S13, the front camera ECU 73 determines whether or not a failurehas been detected through the failure detection process. If it isdetermined that any failure has not been detected, the process moves onto step S14.

In step S14, the front camera ECU 73 controls the imaging device 72 tocapture an image, and acquires the captured image.

In step S15, the front camera ECU 73 analyzes the captured image.Specifically, the front camera ECU 73 performs image processing, animage analysis process, and the like, such as lane detection, pedestriandetection, vehicle detection, headlamp detection, a signal recognitionprocess, and image quality control, and supplies the processing resultsto the ECU 31.

In step S16, in accordance with the analysis process results, the ECU 31controls the steering wheel 33, the headlamp 34, the motor 35, theengine 36, the brake 37, and the display unit 38, to perform variouskinds of driving support processes.

In step S17, the front camera ECU 73 determines whether or not thedriving has been ended. If the driving has not been ended, the processreturns to step S12, and the processing thereafter is repeated. Then, ifit is determined in step S17 that the driving has been ended, theprocess comes to an end.

If it is determined in step S13 that there is a failure, on the otherhand, the process moves on to step S18.

In step S18, the front camera ECU 73 notifies the ECU 31 that a failurehas occurred in the imaging device 72. The ECU 31 terminates the drivingsupport process, and causes the display unit 38 to display an image forcausing the driver to recognize that the driving support has ended andis no longer being provided.

As in the above described process, in a driving support process to beperformed in accordance with an image captured by the imaging device 72,if the driving support process cannot be appropriately performed due toa failure detected in the imaging device 72, the driving support processis immediately ended. Thus, it is possible to prevent an accident or thelike due to an inappropriate driving support process.

<Example Configuration of the Hardware>

Referring now to FIG. 4, the configuration of the hardware of the frontcamera ECU and the imaging device is described. The hardware of thefront camera ECU and the imaging device has a configuration in which alower chip 91 and an upper chip 92 are stacked. Note that, the righthalf of FIG. 4 shows a floor plan that is the hardware configuration ofthe lower chip 91, and the left half of FIG. 4 shows a floor plan thatis the hardware configuration of the upper chip 92.

Through chip vias (TCVs) 93-1 and 93-2 are provided at the right andleft end portions of each of the lower chip 91 and the upper chip 92 inthe drawing, and penetrate through the lower chip 91 and the upper chip92, to electrically connect the lower chip 91 and the upper chip 92. Inthe lower chip 91, a row drive unit 102 (FIG. 5) is disposed to theright of the TCV 93-1 in the drawing, and is electrically connected tothe TCV 93-1. A control line gate 143 (FIG. 5) of the front camera ECU73 is disposed to the left of the TCV 93-2 in the drawing, and iselectrically connected to the TCV 93-2. Note that the row drive unit 102and the control line gate 143 will be described later in detail withreference to FIG. 5.

In addition, TCVs 93-11 and 93-12 are provided at the upper and lowerend portions of each of the lower chip 91 and the upper chip 92 in thedrawing, and penetrate through the lower chip 91 and the upper chip 92,to electrically connect the lower chip 91 and the upper chip 92. In thelower chip 91, a column analog-to-digital converter (ADC) 111-1 isdisposed under the TCV 93-11 in the drawing, and is electricallyconnected to the TCV 93-11. A column analog-to-digital converter (ADC)111-2 is disposed on the TCV 93-12 in the drawing, and is electricallyconnected to the TCV 93-12.

A digital-to-analog converter (DAC) 112 is provided between the rightend portions of the column ADCs 111-1 and 111-2 and on the left side ofthe control line gate 143, and outputs ramp voltages to the column ADCs111-1 and 111-2, as indicated by arrows C1 and C2 in the drawing. Notethat the column ADCs 111-1 and 111-2, and the DAC 112 correspond to animage signal output unit 103 shown in FIG. 5. Also, the DAC 112preferably outputs ramp voltages having the same characteristics to thecolumn ADCs 111-1 and 111-2, and therefore, is preferably located at thesame distance from the column ADCs 111-1 and 111-2. Further, althoughonly one DAC 112 is provided in the example shown in FIG. 4, a DAC maybe provided for each of the column ADCs 111-1 and 111-2. That is, atotal of two DACs having the same characteristics may be provided forthe respective column ADCs 111-1 and 111-2. Note that the image signaloutput unit 103 will be described later in detail with reference to FIG.5.

Furthermore, a signal processing circuit 113 is provided between theupper and lower column ADCs 111-1 and 111-2, and between the row driveunit 102 and the DAC 112, and forms the functions corresponding to acontrol unit 121, an image processing unit 122, an output unit 123, anda failure detector 124 shown in FIG. 5.

In the upper chip 92, substantially the entire surface of therectangular region surrounded by the TCVs 93-1, 93-2, 93-11, and 93-12provided at the upper, lower, right, and left end portions is formedwith a pixel array 101.

In accordance with a control signal supplied from the row drive unit 102from the TCV 93-1 via a pixel control line L (FIG. 5), the pixel array101 outputs the pixel signals of the pixels in the upper half in thedrawing among pixel signals to the lower chip 91 via the TCV 93-11, andoutputs the pixel signals of the pixels of the lower half in the drawingto the lower chip 91 via the TCV 93-12.

As indicated by an arrow B1 in the drawing, the control signal istransmitted from the signal processing circuit 113 that embodies the rowdrive unit 102 to the control line gate 143 (FIG. 5) via the pixelcontrol line L of the pixel array of the upper chip 92 via the TCV 93-1.The control line gate 143 (FIG. 5) detects presence/absence of a failuredue to disconnection of the pixel control line L and the TCVs 93-1 and93-2, by comparing the signal output from the control line gate 143depending on the control signal from the row drive unit 102 (FIG. 5) viathe pixel control line L for the row address that is command informationfrom the control unit 121 (FIG. 5), with the detection pulse of thecontrol signal corresponding to the row address supplied from thecontrol unit 121. As indicated by an arrow B2 in the drawing, thecontrol line gate 143 then outputs information about thepresence/absence of a failure to the failure detector 124 formed withthe signal processing circuit 113.

As indicated by an arrow A1 in the drawing, the column ADC 111-1converts the pixel signals of the pixels of the upper half of the pixelarray 101 in the drawing, which are supplied via the TCV 93-11, intodigital signals column by column, and outputs the digital signals to thesignal processing circuit 113. Also, as indicated by an arrow A2 in thedrawing, the column ADC 111-2 converts the pixel signals of the pixelsof the lower half of the pixel array 101 in the drawing, which aresupplied via the TCV 93-12, into digital signals column by column, andoutputs the digital signals to the signal processing circuit 113.

With this two-layer structure, the upper chip 92 only includes the pixelarray 101, and accordingly, a semiconductor process specialized forpixels can be introduced. For example, since there is no circuittransistor in the upper chip 92, there is no need to pay attention tocharacteristics fluctuation due to a 1000° C. annealing process or thelike, and thus, a high-temperature process or the like for preventingwhite spots can be introduced. As a result, characteristics can beimproved.

Further, the failure detector 124 is disposed in the lower chip 91, sothat signals that have passed through the TCVs 93-1 and 93-2 from thelower chip 91 to the upper chip 92 and from the upper chip 92 to thelower chip 91. Thus, appropriate failure detection can be performed.

<Specific Example Configurations of the Front Camera ECU and the ImagingDevice>

Referring now to FIG. 5, specific example configurations of thefunctions of the front camera ECU 73 and the imaging device 72 formed bythe hardware shown in FIG. 4 are described.

The imaging device 72 includes the pixel array 101, the row drive unit102, and the image signal output unit 103.

In the pixel array 101, pixels that generate pixel signals depending onincident light are arranged in an array.

The row drive unit 102 generates a control signal to be transferred in avertical direction, to reset and accumulate pixel signals from therespective pixels in the pixel array 101, and to read the reset levelsand the signal levels of the pixel signals. The row drive unit 102supplies the control signal to the respective pixels via the pixelcontrol line L, so that the pixel signals are reset and read pixel bypixel.

Note that, in this case, both the reset level in a state where anysignal subjected to photoelectric conversion is not accumulated, and thesignal level in a state where signals subjected to photoelectricconversion are accumulated are read from the pixel signal at each of thepixels. That is, each pixel is read twice, and the difference valuebetween the signal level and the reset level is set as a pixel signal.Accordingly, hereinafter, a pixel signal will be the difference valuebetween the signal level and the reset level.

The image signal output unit 103 converts the pixel signals of analogsignals read out from the pixel array 101 via the TCVs 93-11 and 93-12,under the control of the row drive unit 102, into digital signals, andsupplies the digital signals as pixel signals to the image processingunit 122 of the front camera ECU 73.

The front camera ECU 73 includes the control unit 121, the imageprocessing unit 122, the output unit 123, the failure detector 124, andthe control line gate 143.

The control unit 121 controls operation of the entire front camera ECU73. In a row address selecting function failure detection process, thecontrol unit 121 also supplies command information for designating apredetermined row address to the row drive unit 102 and (the controlline gate 143 of) the failure detector 124.

In a pulse output failure detection process, the control unit 121 alsocontrols the row drive unit 102 to generate a control signal forcontrolling accumulation and reading of the pixel signals of therespective pixels in the pixel array 101. The control unit 121 furthergenerates a pulse for failure detection for each control signal at atime when a control signal is output in the row drive unit 102, andsupplies the pulse to the failure detector 124.

The failure detector 124 includes a row address selecting functionfailure detector 141, a pulse output failure detector 142, and thecontrol line gate 143. The row address selecting function failuredetector 141 performs the row address selecting function failuredetection process, and the pulse output failure detector 142 performsthe pulse output failure detection process, to detect thepresence/absence of a failure and supply the detection result to theoutput unit 123.

More specifically, the row address selecting function failure detector141 detects the presence/absence of a failure in the row addressselecting functions of the row drive unit 102 and the control line gate143, by performing the row address selecting function failure detectionprocess.

The pulse output failure detector 142 also detects the presence/absenceof a pulse output failure of the control signal supplied from the rowdrive unit 102 via the pixel control line L of a predetermined rowaddress, by performing the pulse output failure detection process.

In accordance with an image including an image signal supplied from theimage signal output unit 103 of the imaging device 72, the imageprocessing unit 122 performs image signal processing and an imageanalysis process, such as lane detection, pedestrian detection, vehicledetection, headlamp detection, a signal recognition process, and imagecontrol, for example, and supplies the analysis processing results tothe output unit 123.

The output unit 123 outputs various kinds of processing results from theimage processing unit 122, and the failure detection process result fromthe failure detector 124, to the ECU 31.

Further, the imaging device 72 and the front camera ECU 73 shown in FIG.5 have a structure in which the upper chip 92 serving as a first chipthat forms a surface capable of receiving incident light from theobject, and the lower chip 91 serving as a second chip stacked under theupper chip 92 are electrically connected by the through chip vias (TCVs)93-1, 93-2, 93-11, and 93-12.

More specifically, the left end portion of the pixel array 101 disposedin the upper chip 92 in the drawing, and the row drive unit 102 disposedin the lower chip 91 are electrically connected by the TCV 93-1. Also,the right end portion of the pixel array 101 disposed in the upper chip92 in the drawing, and the control line gate 143 disposed in the lowerchip 91 are electrically connected by the TCV 93-2. Further, the lowerend portion of the pixel array 101 disposed in the upper chip 92 in thedrawing, and the image signal output unit 103 disposed in the lower chip91 are electrically connected by the TCVs 93-11 and 93-12.

In the upper chip 92, only the pixel array 101 of the imaging device 72is disposed. The row drive unit 102 and the image signal output unit 103of the imaging device 72, and the control unit 121, the image processingunit 122, the output unit 123, and the failure detector 124, whichconstitute the front camera ECU 73, are disposed in the lower chip 91.

<Failure Detection Process by the Failure Detector>

Next, the row address selecting function failure detection process atthe row address selecting function failure detector 141 of the failuredetector 124, and the pulse output failure detection process at thepulse output failure detector 142 are described, with reference to FIG.6.

The row address selecting function failure detector 141 is controlled bythe control unit 121, and acquires row address command informationsupplied from the control unit 121. The control unit 121 also suppliesthe same row address command information as that supplied to the rowaddress selecting function failure detector 141, to the row drive unit102 and the control line gate 143.

In accordance with the row address command information supplied from thecontrol unit 121, the row drive unit 102 and the control line gate 143output selection information that is information about the row addressto be selected as the current control target, to the row addressselecting function failure detector 141 and the pulse output failuredetector 142.

The row address selecting function failure detector 141 compares the rowaddress command information supplied from the control unit 121 with therow address selection information supplied from the row drive unit 102and the control line gate 143. If the row address command informationmatches the row address selection information, the row address selectingfunction failure detector 141 determines that there is no failure in therow address selecting function of the row drive unit 102 and the controlline gate 143. If the row address command information does not match therow address selection information, the row address selecting functionfailure detector 141 determines that there is a failure in the rowaddress selecting function.

The pulse output failure detector 142 detects presence/absence of afailure due to disconnection of the pixel control line L and the TCVs93, by comparing the signal output from the control line gate 143depending on the control signal from the row drive unit 102 via thepixel control line L for the row address that is the command informationfrom the control unit 121, with the detection pulse of the controlsignal corresponding to the row address supplied from the control unit121. The configurations of the control line gate 143 and the pulseoutput failure detector 142 will be described later in detail withreference to FIGS. 9 and 10.

Note that the functions of the control unit 121 and the failure detector124 shown in FIG. 6 are formed with the signal processing circuit 113shown in FIG. 5.

<Row Address Selecting Function Failure Detection Processing>

Referring now to the flowchart in FIG. 7, the row address selectingfunction failure detection process to be performed by the control unit121 and the row address selecting function failure detector 141 of thefailure detector 124 is described.

In step S21, the control unit 121 supplies command information fordesignating a predetermined row address to the row drive unit 102 andthe failure detector 124.

Through this process, in step S31, the row address selecting functionfailure detector 141 of the failure detector 124 acquires the commandinformation about the predetermined row address supplied from thecontrol unit 121. In addition, likewise, through the process in stepS51, the row drive unit 102 acquires the command information about thepredetermined row address supplied from the control unit 121.

That is, the process in steps S21 and S31 is the process through a routeR1 shown in FIG. 8, and the process in steps S21 and S51 is the processthrough a route R2 in FIG. 8. Note that, in FIG. 8, the routes throughwhich the information about the predetermined row address is transmittedis indicated with thick lines and arrows.

In step S52, in accordance with the acquired command information aboutthe predetermined row address, the row drive unit 102 supplies thefailure detector 124 with selection information that is the informationabout the row address to be selected as the current target.

In step S32, the row address selecting function failure detector 141acquires the row address information as the selection informationsupplied from the row drive unit 102.

That is, the process in steps S52 and S32 is the process through a routeR3 shown in FIG. 8.

In step S33, the row address selecting function failure detector 141determines whether or not the row address command information matchesthe selection information. If the row address command informationmatches the selection information in step S33, it is determined thatthere is no failure in the row address selecting function of the rowdrive unit 102, and the process comes to an end.

If the row address command information does not match the selectioninformation in step S33, on the other hand, it is determined that afailure has occurred in the row address selecting function, and theprocess moves on to step S34.

In step S34, the row address selecting function failure detector 141detects the occurrence of a failure in the row address selectingfunction at the row drive unit 102, and outputs the detection result tothe output unit 123.

Through the above process, the row address selecting function failuredetector 141 can detect presence/absence of a failure of the row addressselecting function at the row drive unit 102, in accordance with adetermination as to whether or not the information about the row addressthat is the selection information supplied from the row drive unit 102matches the row address that is the command information from the controlunit 121.

Note that the row address selecting function detection process at therow address selecting function failure detector 141 and the control linegate 143 is similar to the process shown in FIG. 7, and therefore,explanation thereof is not made herein. In other words, the control linegate 143 may perform a process similar to the process in steps S51through S53 in FIG. 7, to perform a similar failure detection process.

In this case, the process in steps S21 and S31 is the process throughthe route R1 shown in FIG. 8, and the process in steps S21 and S51 isthe process through a route R4 in FIG. 8. Also, the process in steps S52and S32 is the process through a route R5 shown in FIG. 8.

<Example Configuration of the Control Line Gate>

Referring now to FIG. 9, an example configuration of the control linegate 143 is described.

In the control line gate 143, an address decoder 161, a shutter addresslatch 162, and a read address latch 163 are provided. Also, in therespective rows, switching gates 164 through 168 for detecting thepresence/absence of a supply of a control signal are provided for therespective kinds of control signals required for accumulation andreading of pixel signals. Various kinds of components, such as clockedinverters shown in FIG. 9 or operational amplifiers, can be used as theswitching gates, for example.

The control signals to be dealt with here are the following five kindsof signals: shutter transfer signal Shutter_TRG in each row of the pixelarray, shutter reset signal Shutter_RST in each row, read selectionsignal Read_SEL in each row, read reset signal Read_RST in each row, andread transfer signal Read_TRG in each row.

The shutter transfer signal Shutter_TRG is a control signal for turningon the transfer gate that releases the pixel signals accumulated byphotoelectric conversion from a photodiode. The shutter reset signalShutter_RST is a control signal for turning on the reset gate andsetting the photodiode to the reset level, when releasing the pixelsignals accumulated in the photodiode. The read selection signalRead_SEL is a control signal for turning on the selection gate, whenoutputting the pixel signals accumulated in the FD to a verticaltransfer line (VSL). The read reset signal Read_RST is a control signalfor turning on the reset gate, when setting the FD to the reset level.The read transfer signal Read_TRG is a control signal for turning on thetransfer gate when transferring the pixel signal accumulated in thephotodiode and setting the FD to the signal level.

More specifically, the switching gate 164 detects the shutter transfersignal Shutter_TRG. The switching gate 165 detects the shutter resetsignal Shutter_RST. The switching gate 166 detects the read selectionsignal Read_SEL. The switching gate 167 detects the read reset signalRead_RST. The switching gate 168 detects the read transfer signalRead_TRG. Further, in each row, an inverter 169 that supplies negativepower to the negative supply terminals of the switching gates 164 and165, and an inverter 170 that supplies negative power to the negativesupply terminals of the switching gates 166 through 168 are provided.

The address decoder 161 decodes an address in accordance with addressinformation that is command information supplied from the control unit121, and supplies the decoding result to the shutter address latch 162and the read address latch 163.

The shutter address latch 162 supplies positive power to the positivesupply terminals of the switching gates 164 and 165, and also suppliespower to the inverter 169, when the decoding result is determined to beits own row address. At this stage, the inverter 169 converts thepositive power into negative power, and supplies the negative power tothe negative supply terminals of the switching gates 164 and 165. As aresult, the switching gates 164 and 165 are put into an operable state.

If the switching gate 164 detects the shutter transfer signalShutter_TRG from the row drive unit 102 as a Hi signal in accordancewith the row address that is the corresponding command information atthis stage, the switching gate 164 outputs the corresponding Hi signalto the pulse output failure detector 142 via a STRG bus B5.

Also, if the switching gate 165 detects the shutter reset signalShutter_RST from the row drive unit 102 as a Hi signal, the switchinggate 165 outputs the corresponding Hi signal to the pulse output failuredetector 142 via a SRST bus B4.

The read address latch 163 supplies positive power to the positivesupply terminals of the switching gates 166 through 168, and alsosupplies power to the inverter 170, when the decoding result isdetermined to be its own row address. At this stage, the inverter 170converts the positive power into negative power, and supplies thenegative power to the negative supply terminals of the switching gates166 through 168. As a result, the switching gates 166 through 168 areput into an operable state.

If the switching gate 166 detects the read selection signal Read_SELfrom the row drive unit 102 as a Hi signal in accordance with the rowaddress that is the corresponding command information at this stage, theswitching gate 166 outputs the corresponding Hi signal to the pulseoutput failure detector 142 via a SEL bus B1.

Also, if the switching gate 167 detects the read reset signal Read_RSTas a Hi signal, the switching gate 167 outputs the corresponding Hisignal to the pulse output failure detector 142 via an RRST bus B2.

Further, if the switching gate 168 detects the read transfer signalRead_TRG as a Hi signal, the switching gate 168 outputs thecorresponding Hi signal to the pulse output failure detector 142 via anRTRG bus B3.

That is, when various kinds of control signals corresponding to the rowaddress designated as the command information are correctly suppliedfrom the row drive unit 102, Hi signals are output from thecorresponding buses B1 through B5 at the timing specified by the commandinformation about the row address.

Note that the functions of the control unit 121 and the pulse outputfailure detector 142 shown in FIG. 9 are formed with the signalprocessing circuit 113 in FIG. 4.

<Example Configuration of the Pulse Output Failure Detector>

Referring now to FIG. 10, a specific example configuration of the pulseoutput failure detector 142 is described.

The pulse output failure detector 142 includes a failure determinationunit 181 and latches 182 through 186. When both an output signal fromthe STRG bus B5 and a pulse for detecting the shutter transfer signalSTRG from the control unit 121 enter a Hi signal state, the latch 182outputs a Hi signal to the failure determination unit 181 until a reset.When both an output signal from the SRST bus B4 and a pulse fordetecting the shutter reset signal SRST from the control unit 121 entera Hi signal state, the latch 183 outputs a Hi signal to the failuredetermination unit 181 until a reset.

When both an output signal from the RTRG bus B3 and a pulse fordetecting the read transfer signal RTRG from the control unit 121 entera Hi signal state, the latch 184 outputs a Hi signal to the failuredetermination unit 181 until a reset. When both an output signal fromthe RRST bus B4 and a pulse for detecting the read transfer signal RRSTfrom the control unit 121 enter a Hi signal state, the latch 185 outputsa Hi signal to the failure determination unit 181 until a reset. Whenboth an output signal from the SEL bus B5 and a pulse for detecting theread selection signal SEL from the control unit 121 enter a Hi signalstate, the latch 186 outputs a Hi signal to the failure determinationunit 181 until a reset.

When the output signals of the respective latches 182 through 186 arenot Hi signals, the failure determination unit 181 detects a failure.

Specifically, in a case where each of the latches 182 through 186outputs a Hi signal, the control unit 121 causes the row drive unit 102to output a predetermined control signal indicating the row addressdesignated as command information. In a case where the control signal isappropriately output, the corresponding control signal is output as a Hisignal from the control line gate 143 to the pulse output failuredetector 142 through the buses B1 through B5.

At this timing, the control unit 121 also supplies the pulse outputfailure detector 142 with a pulse for detecting the correspondingcontrol signal that has a greater pulse width than the pulse of thecommand signal for generation of the control signal to be supplied tothe row drive unit 102. Therefore, if those pulses are supplied atalmost the same timing, a Hi signal is output in each of the latches 182through 186. Accordingly, the failure determination unit 181 candetermine that there is no failure, as long as a Hi signal is beingoutput.

If one of the latches 182 through 186 stops outputting a Hi signal inthis case, the control signal at the row address designated as thecommand signal is not output at the designated timing. Accordingly, itcan be determined that a failure due to disconnection has occurred atone of the pixel control lines L or one of the TCVs 93 or the like.

Thus, in a case where any failure is not detected in this process, it isconfirmed that there is no disconnection of the pixel control lines L inthe pixel array 101, and it also can be confirmed that no disconnectionhas occurred in the TCVs 93.

Note that, in each of the latches 182 through 186, a terminal thatreceives reset signals from the control unit 121 is provided, and when areset signal is received prior to operation, the latched value is reset.

Note that the functions of the control unit 121 and the pulse outputfailure detector 142 shown in FIG. 10 are formed with the signalprocessing circuit 113 in FIG. 4.

<Control Line Gate Management Process in the Pulse Output FailureDetection Process>

Referring now to the flowchart in FIG. 11, a control line gatemanagement process in the pulse output failure detection process to beperformed by the control unit 121 and the pulse output failure detector124 is described.

Specifically, in step S61, the control unit 121 supplies a reset signalto all of the latches 182 through 186 in the pulse output failuredetector 142, to reset the latched information. Note that, although onlythe process in each row is described herein, resetting of the latches182 through 186 is performed once in each column. Although only theprocess in each row is described herein, failure detection is alsoperformed on all the rows by repeating a process of detecting a failurewhile one row is being read and reading the next row after a reset.

In step S62, the control unit 121 supplies the control line gate 143with the next control signal to be output from the row drive unit 102and the row address thereof. Note that this process is a process to beperformed individually, when the control signals (Shutter_TRG andShutter_RST) for controlling the shuttering and the control signals(Read_SEL, Read_RST, and Read_TRG) for controlling the reading areoutput to each of the pixels in the pixel array 101.

In step S71, the address decoder 161 of the control line gate 143acquires the control signals and row address information supplied fromthe control unit 121.

In step S72, the address decoder 161 of the control line gate 143decodes the row address information supplied from the control unit 121,and supplies the decoding result to the shutter address latch 162 andthe read address latch 163 of each row.

In step S73, the shutter address latch 162 and the read address latch163 of the corresponding row address each supply electric power to thecorresponding switching gates 164 through 168, and put the switchinggates 164 through 168 into an operable state. More specifically, theshutter address latch 162 and the read address latch 163 each apply apositive voltage to the positive voltage terminals of the switchinggates 164 through 168 of the corresponding row address. The shutteraddress latch 162 and the read address latch 163 also each causegeneration of a negative voltage via the inverters 169 and 170, andapply the negative voltage to the negative voltage terminals of theswitching gates 164 through 168. That is, as a positive voltage and anegative voltage are applied to the positive voltage terminals and thenegative voltage terminals, respectively, the switching gates 164through 168 are put into an operable state.

Here, in step S63, the control unit 121 controls the row drive unit 102so that the shutter transfer signal Shutter_TRG, the shutter resetsignal Shutter_RST, the read selection signal Read_SEL, the read resetsignal Read_RST, and the read transfer signal Read_TRG at the same rowaddress as the row address are output at predetermined timing.

On the other hand, in step S74, the switching gates 164 through 168determine whether or not the corresponding shutter transfer signalShutter_TRG, the corresponding shutter reset signal Shutter_RST, thecorresponding read selection signal Read_SEL, the corresponding readreset signal Read_RST, and the corresponding read transfer signalRead_TRG have been supplied. If these signals have been supplied, theswitching gates 164 through 168 output Hi signals to the correspondingbuses B1 through B5. Note that, for ease of explanation, the switchinggates 164 through 168 determine the presence/absence of the controlsignals independently of one another in this process. However, when thecontrol gates are detected, the switching gates 164 through 168 operateto output Hi signals, and do not actually determine the presence/absenceof the control signals. Therefore, the process in step S74 merelyindicates the operating conditions for the switching gates 164 through168 to output Hi signals.

That is, when the control signals including the shutter transfer signalShutter_TRG, the shutter reset signal Shutter_RST, the read selectionsignal Read_SEL, the read reset signal Read_RST, and the read transfersignal Read_TRG are supplied to the designated row address, theswitching gates 164 through 168 detect these control signals, and outputHi signals from the STRG bus B5, the SRST bus B4, the SEL bus B1, theRRST bus B2, and the RTRG bus B3, respectively.

On the other hand, if the shutter transfer signal Shutter_TRG, theshutter reset signal Shutter_RST, the read selection signal Read_SEL,the read reset signal Read_RST, and the read transfer signal Read_TRGhave not been supplied in step S74, the process moves on to step S76.

In step S76, the switching gates 164 through 168 output low signals tothe corresponding buses B1 through B5, respectively.

In step S64, the control unit 121 then supplies a STRG detection pulseto the latch 182, a SRST detection pulse to the latch 183, a SELdetection pulse to the latch 186, a RRST detection pulse to the latch185, and a RTRG detection pulse to the latch 184. The STRG detectionpulse, the SRST detection pulse, the SEL detection pulse, the RRSTdetection pulse, and the RTRG detection pulse are supplied as the pulsesfor detecting the shutter transfer signal Shutter_TRG, the shutter resetsignal Shutter_RST, the read selection signal Read_SEL, the read resetsignal Read_RST, and the read transfer signal Read_TRG.

Through the above process, under the control of the control unit 121,the row drive unit 102 supplies the control signals that are the shuttertransfer signal Shutter_TRG, the shutter reset signal Shutter_RST, theread selection signal Read_SEL, the read reset signal Read_RST, and aread transfer signal Read_TRG, via the pixel control lines L at apredetermined row address. At this point of time, the control unit 121supplies the STRG detection pulse to the latch 182, the SRST detectionpulse to the latch 183, the SEL detection pulse to the latch 186, theRRST detection pulse to the latch 185, and the RTRG detection pulse tothe latch 184 at the corresponding timing. The STRG detection pulse, theSRST detection pulse, the SEL detection pulse, the RRST detection pulse,and the RTRG detection pulse are supplied as the pulses for detectingthe shutter transfer signal Shutter_TRG, the shutter reset signalShutter_RST, the read selection signal Read_SEL, the read reset signalRead_RST, and the read transfer signal Read_TRG.

<Pulse Output Failure Detection Process>

Next, a pulse output failure detection process to be performed, inconjunction with the above described control line gate managementprocess, by the pulse output failure detector 142 is described withreference to the flowchart in FIG. 12.

In step S91, the latches 182 through 186 determine whether or not therespective detection pulses supplied thereto are Hi signals.Specifically, the latch 182 determines whether or not the STRG detectionpulse is a Hi signal, the latch 183 determines whether or not the SRSTdetection pulse is a Hi signal, the latch 186 determines whether or notthe SEL detection pulse is a Hi signal, the latch 185 determines whetheror not the RRST detection pulse is a Hi signal, and the latch 184determines whether or not the RTRG detection pulse is a Hi signal. Then,if the detection pulses are determined to be Hi signals, the processmoves on to step S92.

In step S92, the latches 182 through 186 determine whether or not thesignals at the buses B5, B4, B3, B2, and B1 are Hi signals.Specifically, the latch 182 determines whether or not the signalsupplied from the STRG bus B5 is a Hi signal, the latch 183 determineswhether or not the signal supplied from the SRST bus B4 is a Hi signal,the latch 186 determines whether or not the signal supplied from the SELbus B1 is a Hi signal, the latch 185 determines whether or not thesignal supplied from the RRST bus B2 is a Hi signal, and the latch 184determines whether or not the signal supplied from the RTRG bus B3 is aHi signal. Then, if the signals at the buses B5, B4, B3, B2, and B1 areHi signals, the process moves on to step S93.

In step S93, the latches 182 through 186 output Hi signals.

Specifically, if the signals at the buses B1 through B5 are Hi signalsas indicated by the period of time from t11 to t12 during a period inwhich the detection pulse is a Hi signal as indicated by the period oftime from t1 to t2 in FIG. 13, the control signals supplied fortransferring a pixel signal via the pixel control lines L at apredetermined row address in the pixel array 101 are appropriatelysupplied at appropriate timing. Accordingly, it is determined that thereis neither a failure due to disconnection or the like of the pixelcontrol lines L and the TCVs 93-1 and 93-2, nor a failure that mightcause an abnormality in time constants or the like. Thus, the latches182 through 186 output Hi signals indicating that there is no failure.

If it is determined in step S91 or S92 that one of the signals is not aHi signal, on the other hand, the process moves on to step S94, and thelatches 182 through 186 output Low signals. That is, it is determinedthat a failure due to disconnection of the pixel control lines L, or afailure that causes an abnormality in time constants or the like hasbeen detected, and the latches 182 through 186 output Low signalsindicating that there is a failure.

In step S95, the failure determination unit 181 determines whether ornot the signals supplied from the latches 182 through 186 are Hisignals. If these signals are not Hi signals, or if these signals areLow signals, an occurrence of a failure is detected in step S96.

If the signals supplied from the latches 182 through 186 are Hi signalsin step S95, on the other hand, it is determined that there is nofailure, and the process in step S96 is skipped.

Through the above process, presence/absence of a pulse output failurecan be detected. In other words, it becomes possible to check whether ornot the control signals at a predetermined row address designated by thecontrol unit 121 have been output to the designated row address atdesignated timing. If the output of the control signals cannot beconfirmed, an occurrence of a failure can be detected.

At this point of time, it is also possible to check presence/absence ofdisconnection of the pixel control lines L, presence/absence of anabnormality in various kinds of time constants or the like, andpresence/absence of a state in which the various control signals arefixed as Hi signals.

Furthermore, only the pixel array 101 in the imaging device 72 isprovided in the upper chip 92, the other components of the imagingdevice 72 and the front camera ECU 73 are provided in the lower chip 91,and the upper chip 92 and the lower chip 91 are stacked and areelectrically connected via the TCVs 93-1 and 93-2. With this structure,it is also possible to check presence/absence of disconnection of theTCVs 93-1 and 93-2.

Note that, in the process in steps S91 and S92 in FIG. 12, the latches182 through 186 determine whether or not the supplied signals are Hisignals. However, the latches 182 through 186 do not actually determinewhether or not the signals are Hi signals. That is, the latches 182through 186 are designed only to output Hi signals when the variousdetection pulses are Hi signals while the signals from the buses B1through B5 are Hi signals. Therefore, the process in steps S91 and S92in FIG. 12 merely indicates the operating conditions for the latches 182through 186 to output Hi signals.

First Modification of the First Embodiment

In the above described example, a pulse output failure detection processis a process in which detection pulses are output to the pulse outputfailure detector 142 at the time when various control signals are outputfrom the control unit 121 to the control line gate 143, and the latches182 through 186 output Hi signals indicating that there is no failureonly in a case where the timing of the various control signals at thecontrol line gate 143 matches the timing of the output signals from thebuses B1 through B5. However, all the detection pulses may be fixed Hisignals, and presence/absence of signals from the buses B1 through B5may be checked, so that only failures due to disconnection of the pixelcontrol lines L and the TCVs 93-1 and 93-2 are detected in a simplermanner.

FIG. 14 shows an example configuration of the pulse output failuredetector 142 having a simplified structure. Note that, in theconfiguration of the pulse output failure detector 142 shown in FIG. 14,the components having the same functions as the components in the pulseoutput failure detector 142 shown in FIG. 10 are denoted by the samereference numerals and signs, and have the same names as those in FIG.10. Therefore, explanation of them will not be repeated below, asappropriate.

Specifically, the pulse output failure detector 142 in FIG. 14 differsfrom the pulse output failure detector 142 in FIG. 10 in that latches191 through 195 having the same structure are provided in place of thelatches 182 through 186, and a detection pulse is shared among thelatches 191 through 195 and is supplied as a fixed Hi signal. Further,the control unit 121 supplies a reset pulse (RST pulse) to the latches191 through 195 once in each process for one row in the horizontaldirection, and thus, resets the respective latches.

With such a configuration, a pulse output failure due to disconnectionor the like can be detected in a simple manner through the abovedescribed control line gate management process, in accordance with Hisignals or Low signals of the buses B1 through B5 indicatingpresence/absence of control signals supplied via the pixel control linesL and the TCVs 93-1 and 93-2.

Note that the functions of the control unit 121 and the pulse outputfailure detector 142 shown in FIG. 14 are formed with the signalprocessing circuit 113 in FIG. 4.

<Pulse Output Failure Detection Process by the Pulse Output FailureDetector in FIG. 14>

Referring now to the flowchart in FIG. 15, a pulse output failuredetection process by the pulse output failure detector shown in FIG. 14is described. Note that this process will be described below on theassumption that the control line gate management process described withreference to the flowchart in FIG. 11 is performed. In this example,however, the detection pulses in the process in step S63 in FIG. 11 arenot output at predetermined timings for the respective control signals,but are invariably output as Hi signals.

In step S111, the latches 191 through 195 determine whether or not thesignals supplied from the corresponding buses B5, B4, B3, B2, and B1 areHi signals, or whether or not the signals indicate that control signalshave been supplied thereto. If it is determined in step S111 that the Hisignals have been supplied, the process moves on to step S112.

In step S112, since the detection pulses are fixed Hi signals, and thesignals supplied from the corresponding buses B5, B4, B3, B2, and B1 areHi signals, the latches 191 through 195 latch Hi signals indicating thatno failure has been detected, and output the Hi signals.

If the signals supplied from the corresponding buses B5, B4, B3, B2, andB1 are Low signals in step S111, on the other hand, the control signalshave been supplied, and therefore, it is determined that a failure suchas disconnection has been detected. The process then moves on to stepS113.

In step S113, the latches 191 through 195 latch and output Low signalsindicating that a failure has been detected.

In step S114, the failure determination unit 181 determines whether ornot a Low signal has been supplied from any of the latches 191 through195. Then, if it is determined in step S114 that a Low signal has beensupplied, the process moves on to step S115.

In step S115, the failure determination unit 181 determines that afailure has been detected, and outputs information indicating that afailure has occurred.

Through the above process, it is possible to detect, with a simpleconfiguration, a failure related to disconnection of the pixel controllines L and the TCVs 93-1 and 93-2 in the pixel array 101.

Second Modification of the First Embodiment

In the above described example, the row drive unit 102 and the controlline gate 143 are connected via the TCVs 93-1 and 93-2, with the pixelarray 101 being interposed in between. However, the area in which theTCVs 93 are provided may be minimized, to reduce the total area of theupper chip 92 and the lower chip 91.

In this case, as shown in a left portion of FIG. 16, the control linegate 143 may be disposed between the pixel array 101 and the row driveunit 102, and a TCV 93 may be provided only between the pixel array 101and the control line gate 143, for example.

With such a configuration, the portion at which the TCV 93 is providedcan be reduced, and accordingly, the area relating to the TCV 93 can bereduced. Further, processing in the control line gate 143 can realizesimilar processing to that in the case shown in FIG. 4, and thus, it ispossible to check whether the control signals output from the row driveunit 102 are output to a predetermined row address at predeterminedtimings.

However, where only this configuration is adopted, it is not possible tocheck presence/absence of disconnection of the pixel control line L andthe TCV 93 in the pixel array 101.

Therefore, in the pixel array 101 shown in FIG. 16, a failure detectioncolumn 201 formed with black pixels (optical black pixels) is providedat the right end portion, and a series of controls signals necessary forreading a normal pixel signal are supplied for a predetermined rowaddress. In this manner, a predetermined pixel value is generated, andis output to a pixel control line failure detector 202 provided in thefailure detector 124. In accordance with the signal supplied from thefailure detection column 201, the image control line failure detector202 detects a failure related to disconnection of the pixel control lineL and the TCV 93.

More specifically, as shown in a right portion of FIG. 16, the failuredetection column 201 is formed with optical black (OPB) pixels notincluding any photodiode. As a series of control signals designated by apredetermined row address are supplied, a predetermined pixel signalcorresponding to a black pixel is output. In FIG. 16, the portion atwhich a photodiode is normally disposed is denoted by the circuit symbolof a photodiode with a dotted line, which indicates that any photodiodeis not provided.

More specifically, the failure detection column 201 includes a transfertransistor 211, a reset transistor 212, a floating diffusion (FD) 213,an amplification transistor 214, a selection transistor 215, and an ADconverter 216.

The transfer transistor 211, the reset transistor 212, the amplificationtransistor 213, and the selection transistor 215 are all provided in aconventional pixel circuit, and are operated with the shutter transfersignal Shutter_TRG, the shutter reset signal Shutter_RST, the readselection signal Read_SEL, the read reset signal Read_RST, and the readtransfer signal Read_TRG, which have been described above.

In addition, the pixel signal of a black pixel output from the selectiontransistor 215 is output to the AD converter 216. The AD converter 216performs analog-to-digital conversion on the pixel signal, and outputsthe pixel signal to the pixel control line failure detector 202.

Depending on whether or not the pixel signal supplied from the failuredetection column 201 indicates the pixel value of a predetermined blackpixel, the pixel control line failure detector 202 detectspresence/absence of a failure related to disconnection of the pixelcontrol lines L and the TCVs 93 in the pixel array 101.

Note that, although an example configuration not including anyphotodiode has been described as the configuration of the failuredetection column 201, any configuration may be adopted in principle, aslong as a fixed pixel value is output when a pixel signal is read out.For example, a photodiode may be disposed at the portion indicated bythe dotted line in FIG. 16, to block light. A pixel circuit of blackpixels may be formed in this manner.

Note that the functions of the control unit 121 and the failure detector124 shown in FIG. 16 are formed with the signal processing circuit 113shown in FIG. 4.

<Pixel Control Line Failure Detection Process>

Referring now to the flowchart in FIG. 17, a control line failuredetection process to be performed by the failure detection column 201 ofthe pixel array 101 and the pixel control line failure detector 202shown in FIG. 16 is described.

In step S131, the transistors 211 through 214 in the failure detectioncolumn 201 output a pixel signal of a black pixel, to the AD converter216, as an OPB pixel without any photodiode, in accordance with controlsignals such as the shutter transfer signal Shutter_TRG, the shutterreset signal Shutter_RST, the read selection signal Read_SEL, the readreset signal Read_RST, and the read transfer signal Read_TRG.

In step S132, the AD converter 216 converts the pixel signal formed withan analog signal into a digital signal, and outputs the digital signalto the pixel control line failure detector 202.

In step S133, the pixel control line failure detector 202 determineswhether or not the pixel value of the pixel signal formed with a blackpixel is a predetermined pixel value. If the pixel value is determinednot to be the predetermined pixel value in step S133, the process moveson to step S134.

In step S134, the pixel control line failure detector 202 determinesthat a failure due to disconnection or the like has been detected in thepixel control lines L or the TCVs 93 or the like in the pixel array 101,and outputs the result to the output unit 123.

Specifically, when a pixel control line L or a TCV 93 is disconnected,the transistors 211 through 214 cannot be operated with control signalssuch as the shutter transfer signal Shutter_TRG, the shutter resetsignal Shutter_RST, the read selection signal Read_SEL, the read resetsignal Read_RST, and the read transfer signal Read_TRG. Therefore, it isdetermined that the predetermined pixel value has not been output, and afailure has been detected.

If the predetermined pixel value is detected in step S133, on the otherhand, the process in step S134 is skipped. Specifically, thepredetermined black pixel is detected because the transistors 211through 214 are operated with control signals such as the shuttertransfer signal Shutter_TRG, the shutter reset signal Shutter_RST, theread selection signal Read_SEL, the read reset signal Read_RST, and theread transfer signal Read_TRG. Therefore, it is determined that anyfailure has not been detected.

Through the above process, it becomes possible to perform failuredetection based on the timings at which the control signals output fromthe row drive unit 102 are output and the row address, while reducingthe area occupied by the TCV 93. Further, at this point of time, itbecomes possible to detect a failure due to disconnection of the pixelcontrol lines L and the TCVs 93 in the pixel array 101.

2. Second Embodiment

In the above described example, row address selecting function failures,pulse output failures, and disconnection failures in pixel control linesand TCVs are detected. However, a failure in an analog-to-digitalconversion circuit (ADC) may be detected so that a disconnection failurein a TCV is also detected.

FIG. 18 is a diagram for explaining example configurations of theimaging device 72 and the front camera ECU 73 that are designed todetect disconnection failures of an ADC and a TCV, or more particularlyexample configurations of the pixel array 101, the image signal outputunit 103, and the failure detector 124. Note that, among the componentsshown in FIG. 18, the components having the same functions as thosedescribed with reference to FIG. 4 are given the same names and the samereference numerals as those shown in FIG. 4, and explanation of them isnot made herein as appropriate. The components not particularlymentioned herein are the same as those shown in FIG. 4.

Specifically, the pixel array 101, the image signal output unit 103 andthe failure detector 124 shown in FIG. 18 differs from the configurationshown in FIG. 4 in that the configuration of the pixel circuit of eachof the pixels constituting the pixel array 101 and the configuration ofthe pixel signal output unit 103 are specifically shown, and an ADC+TCVfailure detector 271 is added to the failure detector 124.

The pixel circuit of each of the pixels 221 arranged in an array thatforms the pixel array 101 include a photodiode 230, a transfertransistor 231, a reset transistor 232, a floating diffusion (FD) 233,an amplification transistor 234, a selection transistor 235, and avertical transfer line VSL.

Further, the vertical transfer line VSL is provided with a DSF circuit250 that includes a switch transistor 251 and a DSF transistor 252. Notethat the DSF circuit 250 including the switch transistor 251 and the DSFtransistor 252 is not disposed in the pixel array 101 in the upper chip92 but is disposed in the lower chip 91, and is connected to thevertical transfer line VSL via a TCV 93.

The configuration formed with the photodiode 230, the transfertransistor 231, the reset transistor 232, the floating diffusion (DF)233, the amplification transistor 234, and the selection transistor 235is similar to that of a conventional pixel circuit, and is similar tothat of the pixel circuit forming each of the pixels arranged in anarray in the above described pixel array 101.

Specifically, the photodiode 230 accumulates an electric chargecorresponding to the amount of incident light, and outputs the electriccharge as a pixel signal. The transfer transistor 231 operates with theabove described shutter transfer signal Shutter_TRG and read transferRead_TRG, and transfers the electric charge accumulated in thephotodiode 230 to the FD 233, or cooperates with the reset transistor232 to reset the photodiode 230 and the FD 233 to the reset level.Meanwhile, the reset transistor 232 operates with the above describedshutter reset signal Shutter_RST and read reset signal Read_RST, to setthe FD 233 to the reset level, or to set the photodiode 230 to the resetlevel.

The FD 233 is set to the signal level of the pixel signal supplied fromthe photodiode 230 or to the reset level by the reset transistor 232,and is connected to the gate of the amplification transistor 234.

The amplification transistor 234 amplifies the power supply voltage inaccordance with the voltage of the accumulated electric charge in the FD233, to output a pixel signal. The selection transistor 235 operateswith the read selection signal Read_SEL, and, when selected as a rowaddress, causes the pixel signal output from the amplificationtransistor 234 to be transferred to the vertical transfer line VSL.

In this example, the DSF circuit 250 including the switch transistor 251and the DSF transistor 252 is further provided in the vertical transferline VSL. The DSF circuit 250 outputs a pixel signal or a dummy pixelsignal. More specifically, the DSF (Dummy Source Follower circuit)transistor 252 is a transistor for supplying the vertical transfer lineVSL with a dummy pixel signal that is formed with a fixed signal insteadof a pixel signal. The switch transistor 251 switches between outputtinga pixel signal from the selection transistor 235 to the verticaltransfer line VSL and outputting a dummy pixel signal from the DSFtransistor 252 to the vertical transfer line VSL.

Note that the dummy pixel signal that is output when the DSF transistor252 is turned on is a pixel signal formed with a predetermined pixelvalue. However, a plurality of DSF transistors 252 may be provided tooutput a plurality of pixel signals formed with predetermined pixelvalues in a switching manner. In the description below, a plurality ofDSF transistors 252 that are not shown in the drawing are provided forthe respective pixel signals formed with a plurality of kinds of pixelvalues, and these pixel signals can be selectively switched and output.

The image signal output unit 103 includes a load MOS 241, an ADC 242,and a horizontal transfer unit 243.

The load MOS 241 converts a pixel signal supplied via the verticaltransfer line VSL of the pixel array 101 from a current value to avoltage value, and supplies the converted value to the ADC 242.

The ADC 242 converts the pixel signal formed with an analog signalsupplied from the load MOS 241 into a digital signal, and outputs thedigital signal to the horizontal transfer unit 243.

More specifically, the ADC 242 includes a comparator 261, a counter 262,and a digital-to-analog converter (DAC) 263.

The comparator 261 performs a comparison between a ramp voltage (Ramp)that is supplied from the DAC 263 and varies at predetermined stepintervals in synchronism with a clock from the counter 262, and a pixelsignal formed with the analog signal input from the load MOS 241. Thecomparator 261 then supplies the comparison result to the counter 262.

The counter 262 repeatedly performs counting, and outputs the countvalue at a time when the comparison result in the comparator 261 isinverted as a digital signal to the horizontal transfer unit 243. Thecounter 262 also supplies a clock signal to the DAC 242.

The DAC 263 generates a ramp voltage (Ramp) by changing the ramp voltageat a predetermined step in synchronization with the clock signal fromthe counter 262, and supplies the ramp voltage to the comparator 261.Note that the DAC 263 corresponds to the DAC 112 in the floor plan inFIG. 4.

The horizontal transfer unit 243 supplies the image processing unit 122with the pixel signal converted to the digital signal supplied from theADC 242, and also supplies the pixel signal to the ADC+TVC failuredetector 271 in the failure detector 124.

The ADC+TVC failure detector 271 controls the DSF circuit 250 to outputa dummy pixel signal during a blanking period or the like, for example,and compares the pixel signal converted to a digital signal by the ADC242 with a predetermined pixel signal that is set as the dummy pixelsignal in advance. Depending on whether or not the converted pixelsignal matches the predetermined pixel signal, the ADC+TCV failuredetector 271 detects a failure in the ADC 242, or a failure due to thepresence of disconnection of the pixel control line L and the TCV 93 orthe like.

More specifically, as shown in FIG. 19, for example, the lower chip 91is divided into two regions formed with lower chips 91-1 and 91-2, andADCs 242-1 and 242-2 are arranged in a column. Further, the lower chips91-1 and 91-2 are electrically connected to the upper chip 92 in whichthe pixel array 101 shown in FIG. 18 is provided, via TCVs 93-11 and93-12, respectively. Here, the ADCs 242-1 and 242-2 shown in FIG. 19correspond to the column ADCs 111-1 and 111-2 in FIG. 4.

In addition, the outputs of the pixels 221 are controlled by row controllines 282-1, 282-2, . . . . A row drive unit 272 performs control sothat the pixel signals of the pixels 221 in a predetermined row areoutput. The pixel signals output from the pixels 221 transmit throughcolumn signal lines 281-1, 281-2, . . . , and are output to the columnADCs 242-1 and 242-2.

Meanwhile, DSF circuits 250-1 (250-1-1, 250-1-2, . . . ) are provided inthe lower chip 91-1, and supply a dummy pixel signal to ADCs 242-2(242-2-1, 242-2-2, . . . ) of the other lower chip 91-2 via the TCVs93-11 and 93-12 and the pixel array 101. Likewise, DSF circuits 250-2(250-2-1, 250-2-2, . . . ) are provided in the lower chip 91-2, andsupply a dummy pixel signal to ADCs 242-1 (242-1-1, 242-1-2, . . . ) ofthe other lower chip 91-1 via the TCVs 93-11 and 93-12 and the pixelarray 101. Note that the number of divisions of the lower chip 91 may betwo or more. In this case, the same number of ADCs 242 and the samenumber of DSF circuits 250 as the number of divisions are provided inthe respective divided regions.

The ADCs 242-1 (242-1-1, 242-1-2, . . . ) each compare the magnitude ofa pixel signal output from the pixel array 101 with the magnitude of aramp voltage supplied from a DAC 263-1 with comparators 261-1 (261-1-1,261-1-2, . . . ), and gives a binary result to counters 262-1 (262-1-1,262-1-2, . . . ).

The ADCs 242-2 (242-2-1, 242-2-2, . . . ) each compare the magnitude ofa pixel signal output from the pixel array 101 with the magnitude of aramp voltage supplied from a DAC 263-2 with comparators 261-2 (261-2-1,261-2-2, . . . ), and gives a binary result to counters 262-2 (262-2-1,262-2-2, . . . ).

The comparators 261-1 and 261-2 have auto zero circuits that use a PSETsignal supplied from a timing control circuit 273 as a trigger, and setan offset that is the difference in level between the pixel signalsupplied from the pixels 221 and the ramp voltage to zero.

The counters 262-1 and 262-2 perform a counting operation in accordancewith a counter control signal supplied from the timing control circuit273. The counter clock is masked by the outputs of the comparators 261-1and 261-2, so that a digital signal corresponding to the level of thepixel signal can be obtained.

Bus buffers 274-1 (274-1-1, 274-1-2, . . . ) are designed forcontrolling outputs, and include latch circuits. The bus buffers 274-1each output a value to a horizontal output line 276-1, in accordancewith a selection signal from a column scan circuit 275-1.

Bus buffers 274-2 (274-2-1, 274-2-2, . . . ) are designed forcontrolling outputs, and include latch circuits. The bus buffers 274-2each output a value to a horizontal output line 276-2, in accordancewith a selection signal from a column scan circuit 275-2.

The timing control circuit 273 controls the overall operation sequencein the imaging device 72, with a master clock MCK being the operationtiming reference.

The ADC+TVC failure detector 271 controls the DSF circuits 250-1 and250-2 to output a dummy pixel signal via the pixel array 101 and theTCVs 93-11 and 93-12, and causes the ADCs 242-1 and 242-2 to convert apixel signal into a digital signal. Depending on whether or not thepixel signal is formed with a predetermined pixel value, the ADC+TCVfailure detector 271 detects an abnormality in the ADCs 242-1 and 242-2and a failure due to disconnection of the TCVs 93-11 and 93-12.

More specifically, the ADC+TVC failure detector 271 controls the DSFcircuits 250-1 of the lower chip 91-1, so that a dummy pixel signal isoutput to the ADCs 242-2 of the lower chip 91-2 via the pixel array 101and the TCVs 93-11 and 93-12, and the ADCs 242-2 convert a pixel signalinto a digital signal. Depending on whether or not the pixel signal isformed with a predetermined pixel value, the ADC+TCV failure detector271 detects an abnormality in the ADCs 242-2 and a failure due todisconnection of the TCVs 93-11 and 93-12.

Likewise, the ADC+TVC failure detector 271 controls the DSF circuits250-2 of the lower chip 91-2, so that a dummy pixel signal is output tothe ADCs 242-1 of the lower chip 91-1 via the pixel array 101 and theTCVs 93-11 and 93-12, and the ADCs 242-1 convert a pixel signal into adigital signal. Depending on whether or not the pixel signal is formedwith a predetermined pixel value, the ADC+TCV failure detector 271detects an abnormality in the ADCs 242-1 and a failure due todisconnection of the TCVs 93-11 and 93-12.

Furthermore, an operation test on mounting may be further conducted todetect a failure as an operation abnormality, on the premise that thereis no abnormalities in the ADCs 242 and the TCVs 93.

<First Operation Test>

As shown in FIG. 20, for example, the ADC+TVC failure detector 271controls the DSF circuit 250, to realize the following series ofoperations: a dummy pixel signal formed with a potential V1 at the resetlevel is generated, and the ADC 242 obtains a pixel signal at the resetlevel; and a dummy pixel signal formed with a potential V2 at apredetermined signal level for the potential of the DSF circuit 250, anda pixel signal at the signal level is obtained. The ADC+TCV failuredetector 271 may detect an operation failure by checking whether or nota pixel signal that is the difference between the signal level and thereset level is output as a predetermined pixel signal.

In this manner, it is possible to perform failure detection based onwhether or not an abnormality has occurred in the reading of a pixelsignal by correlated double sampling.

Note that, in FIG. 20, the solid line indicates the pixel value of thedummy pixel signal that is output by controlling the DSF circuit 250,and the dashed line indicates the change in the ramp voltage. Betweentime t0 and time t2, the potential V1 at the reset level is output asthe dummy pixel signal, and the ramp potential becomes lower during thisperiod. At the timing indicated by a circle between time t0 and time t1,the comparison result from the comparator 261 inverts. Accordingly, atthis timing, a pixel signal formed with a digital signal at the resetlevel is obtained from the value of the counter at the ramp voltagecorresponding to the reset level potential V1.

In addition, at time t3, the DSF circuit 250 is controlled, and a dummypixel signal corresponding to the potential V2 is output as a pixelsignal at the signal level. The ramp voltage is reset at time t4, andfalls again between time t4 and time t5. As the comparison result fromthe comparator 261 inverts at the timing indicated by a circle betweentime t4 and t5, a pixel signal formed with a digital signal at thesignal level is output at this timing.

If the difference between the reset level and the signal level obtainedin this manner is obtained as a pixel value, and the pixel value is apredetermined pixel value that has been set in advance, there is nofailure due to disconnection of the ADC 242 and the TCV 93. Further, itis also possible to confirm that any operation failure has occurred in apixel signal reading process by CDS.

Note that the pixel value of the dummy pixel signal that is indicated bythe solid line in FIG. 20 and is output through control of the DSFcircuit 250 is output from the pixel array 101 in the floor plan in FIG.4. Also, the ramp voltage indicated by the dashed line in FIG. 20 isoutput by the DAC 111 in the floor plan in FIG. 4. That is, the DAC 263corresponds to the DAC 111.

<Second Operation Test>

The gain in analog-to-digital conversion may be changed to obtain an ADconversion result, and an operation failure due to a gain error may bedetected.

As shown in FIG. 21, the step width of the ramp voltage is changed, andthe value of the counter is multiplied by the analog gain. In thismanner, an AD conversion result is checked.

Specifically, as shown in FIG. 21, the step width that is the rate ofchange in the ramp voltage is changed, and each AD conversion result ischecked to determine whether each signal has been converted into apredetermined digital signal. For example, at time t3, the operation ofthe DSF circuit 250 is controlled, so that a dummy pixel signalcorresponding to the potential V2 is output.

At this point of time, an operation failure due to a gain error may bedetected, depending on whether or not the pixel signal converted intothe digital signal obtained at time t11 through the change in a 0-dBramp voltage that is indicated by a dashed line in FIG. 21, for example,and the pixel signal converted into the digital signal obtained at timet12 through the change in a 30-dB ramp voltage indicated by adot-and-dash line, for example, match respective pixel signals that havebeen set in advance.

Note that the pixel value of the dummy pixel signal that is indicated bythe solid line in FIG. 21 and is output through control of the DSFcircuit 250 is output from the pixel array 101 in the floor plan in FIG.4. Also, the ramp voltage indicated by the dashed line in FIG. 21 isoutput by the DAC 111 in the floor plan in FIG. 4. That is, the DAC 263corresponds to the DAC 111.

<Third Operation Test>

To detect an operation failure, a check may be made to determine whetheror not an operation for a sunspot correction process is performed.

In a case where a sunspot appears, a pixel signal at the reset levelcannot be obtained. In such a case, the signal level corrects the pixelsignal by counting the value of the counter to the maximum value.

Therefore, as shown in FIG. 22, at the time t21, which is before thet1-t2 period for determining the reset level, the operation of the DSFcircuit 250 is controlled, so that a dummy pixel signal formed with apotential V11 that cannot be set at the reset level is output. Afterthat, in a case where a pixel signal at the signal level is detectedafter time t4, a check is made at time t23 to determine whether or not asunspot correction process is to be performed, depending on whether ornot to perform an operation to count the counter value up to the maximumvalue, even if the comparator inverts at time t22, as will be shownthereafter. In this manner, an operation failure is detected.

Note that the pixel value of the dummy pixel signal that is indicated bythe solid line in FIG. 22 and is output through control of the DSFcircuit 250 is output from the pixel array 101 in the floor plan in FIG.4. Also, the ramp voltage indicated by the dashed line in FIG. 22 isoutput by the DAC 111 in the floor plan in FIG. 4. That is, the DAC 263corresponds to the DAC 111.

<Fourth Operation Test>

To detect an operation failure, a check may be made to determine whetheror not a clamp operation at a time of dark-current clamp is performed.

Specifically, in a case where there is noise due to dark current, thevalue for the ramp voltage is clamped by the amount equivalent to thepixel signal formed with the noise due to the dark current. Thus, thepixel signal is corrected.

Therefore, as shown in FIG. 23, after the reset level at time t2 isdetected, a dummy pixel signal is set to a pixel signal V21 that is suchthat a pixel signal with the maximum clamp value Cmax can be detected.An operation failure may be then detected, depending on whether or not apredetermined digital signal is obtained, and a clamp operation is to beperformed.

Note that the pixel value of the dummy pixel signal that is indicated bythe solid line in FIG. 23 and is output through control of the DSFcircuit 250 is output from the pixel array 101 in the floor plan in FIG.4. Also, the ramp voltage indicated by the dashed line in FIG. 23 isoutput by the DAC 111 in the floor plan in FIG. 4. That is, the DAC 263corresponds to the DAC 111.

<ADC+TCV Failure Detection Process>

Referring now to the flowchart in FIG. 24, an ADC+TCV failure detectionprocess to be performed by the ADC+TCV failure detector 271 isdescribed.

In step S151, the ADC+TCV failure detector 271 determines whether or nota blanking period in image processing has started, and repeats a similarprocess until a blanking period starts. Then, if a blanking period hasstarted in step S151, the process moves on to step S152.

In step S152, the ADC+TCV failure detector 271 operates the DSF circuit250-1 at a predetermined column address, so that a dummy pixel signal isoutput while being changed in time series to comply with one of theabove described first through fourth operation tests.

In step S153, the ADC 242-2 converts the pixel signal output as thedummy pixel signal into a digital signal, and sequentially supplies thedigital signal to the ADC+TCV failure detector 271.

In step S154, in accordance with the time-series change in the pixelsignal that has been output as the dummy pixel signal supplied from theADCs 242-2 and been converted into a digital signal, the ADC+TCV failuredetector 271 determines whether or not a predetermined operation resulthas been obtained from an operation test among the above described firstthrough fourth operation tests. If a predetermined operation result hasnot been obtained from an operation test among the first through fourthoperation tests in step S154, the process moves on to step S155.

In step S155, the ADC+TCV failure detector 271 detects an operationalabnormality in the ADCs 242-2 and a disconnection failure in the TCVs93-11 and 93-12, or an operation failure related to an operation checkedby the first through fourth operation tests, and supplies the detectionresult to the output unit 123.

If a predetermined operation result has been obtained from an operationrest among the first through fourth operation tests in step S154, on theother hand, it is determined that neither disconnection failures in theADCs 242-2 and the TCVs 93-11 and 93-12, nor operation failures relatedto an operation checked by an operation test among the first throughfourth operation tests have occurred. Therefore, the process in stepS155 is skipped.

Through the above described process, it becomes possible to detectpresence/absence of an operational abnormality in the ADCs 242,presence/absence of disconnection of the TCVs 93, and presence/absenceof an operation failure checked by the first through fourth operationtests.

Note that, in the above described example, one of the above describedfirst through fourth operation tests is conducted during a blankingperiod. However, the first through fourth operation tests may besequentially switched and performed every time a blanking period starts,or two or more of these operation tests may be performed during oneblanking period, for example.

Also, in the above described example, the DSF circuits 250-1 arecontrolled to generate dummy pixel signals, and pixel signals aresubjected to AD conversion by the ADCs 242-2. However, it is of coursepossible to control the DSF circuits 250-2 so that dummy pixel signalsare generated, and pixel signals are subjected to AD conversion by theADCs 242-1.

First Modification of the Second Embodiment

In the above described example, the set potentials of dummy pixelsignals that can be controlled by the DSF circuit 250 are set at thesame potential in the vertical transfer line VSL of each column.However, different pixel potentials may be set. For example, as shown inFIG. 25, the dummy pixel signals in the VSLs indicated by dotted linesand the VSLs indicated by solid lines in columns adjacent to one anothermay be alternately set at a first potential and a second potential thatis higher than the first potential. When short-circuiting occurs betweenthe adjacent vertical transfer lines VSL in such a configuration, thepixel value of a pixel signal converted into a digital signal by the ADC242 changes. Thus, the short-circuiting between the vertical transferlines VSL can be detected.

Note that, in the above described example, the pixel array 101, the rowdrive unit 102, and the image signal output unit 103 are provided as thecomponents of the imaging device 72, while the control unit 121, theimage processing unit 122, the output unit 123, the failure detector124, and the control line gate 143 are provided as the components of thefront camera ECU 73. However, in addition to the pixel array 101, therow drive unit 102, and the image signal output unit 103, the controlunit 121 (or only the function related to failure detection among thefunctions thereof), the failure detector 124, and the control line gate143 may also be provided as the components of the imaging device 72. Asthe imaging device 72 is made to have some of the functions of the frontcamera ECU 73 in this manner, failure detection can be singly performedby the imaging device 72. Further, it is also possible to replace aconventional imaging device with the imaging device 72 of the presentdisclosure. Thus, failure detection becomes possible even in a machinethat used to have no imaging device capable of failure detection.

3. Third Embodiment

In the example described in the first embodiment, driving support isended when a failure is detected through a driving support process.However, even if a failure is detected, the portion with the failure maybe corrected or the like so that the driving support can be continued.

Specifically, the ADCs 242 are formed on a column-by-column basis.Therefore, in a case where a failure occurs in a column, noise isincluded in pixel signals in the row or the column having the failure,resulting in vertical streak noise or horizontal streak noise.

To counter that in such a case, the pixel signals of the row or thecolumn where a failure has been detected are corrected with the pixelsignals of rows or columns having no failures. In this manner, a failureoccurrence may be solved by correction so that the driving supportprocess can be continued.

FIG. 26 shows an example configuration of an imaging device 72 designedto be capable of correction and output in a case where vertical streaknoise or horizontal streak noise has appeared due to an abnormality inthe ADCs 242 that perform AD conversion column by column. Note thatcomponents such as the row drive unit 102 related to control are notshown in the configuration of the imaging device 72 in FIG. 26.

Specifically, the imaging device 72 in FIG. 26 includes a pixel array101, an image signal output unit 103, and a correction unit 301.Although the configuration of one column is shown in FIG. 26, the ADCs242 for all the columns are provided in practice, and pixel signals ofthe respective columns are converted into digital signals by the ADCs242. The digital signals are then output to the correction unit 301.Note that, in the image signal output unit 103 shown in FIG. 26, theconfiguration of the ADC 242 described above with reference to FIG. 18is shown in a simplified manner, and only the configuration of onecolumn is shown.

The correction unit 301 detects presence/absence of an occurrence of afailure by detecting presence/absence of horizontal streak noise andvertical streak noise. In a case where there is a failure, thecorrection unit 301 outputs a signal indicating an occurrence of anerror from an error pin to the MCU 74.

Further, in a case where horizontal streak noise or vertical streaknoise has been detected, the correction unit 301 uses the pixel signalsof normal rows and the pixel signals of normal columns in correcting thepixels signals of the row and the pixel signals of the column causingthe horizontal streak noise and the vertical streak noise, so that thecorrected pixel signals are output. Note that an example configurationof the correction unit 301 will be described in detail with reference toFIG. 27.

<Example Configuration of the Correcting Unit>

Referring now to FIG. 27, an example configuration of the correctionunit 301 is described.

The correction unit 301 includes a buffer 330, a horizontal streakcorrection processing unit 331, a vertical streak correction processingunit 332, a selection unit 333, and a selector 334.

The buffer 330 stores pixel signals supplied from the image signaloutput unit 103, and stores the pixel signals as one image.

The horizontal streak correction processing unit 331 sets the pixelsignals stored in the buffer 330 as current target rows one by one. Thehorizontal streak correction processing unit 331 reads the pixel signalsof the pixels of the three rows including the current target row and therows before and after the current target row, and calculates the averagevalue of each of the three rows. The horizontal streak correctionprocessing unit 331 then calculates the difference between the averagevalue of the pixel signals of the current target row and the averagevalue of the pixel signals of the other rows, and determines whether ornot there is horizontal streak noise by determining whether or not thedifference is larger than a predetermined value. The horizontal streakcorrection processing unit 331 outputs the determination result to theselection unit 333, and, if there is horizontal streak noise, performscorrection by replacing each pixel value of the current target row withthe average value of the pixel values of the rows before and after thecurrent target row.

The vertical streak correction processing unit 332 sets the pixelsignals stored in a buffer 354 of the horizontal streak correctionprocessing unit 331 as current target columns one by one. The verticalstreak correction processing unit 332 reads the pixel signals of thepixels of the three columns including the current target column and thecolumns before and after the current target column, and calculates theaverage value of each of the three columns. The vertical streakcorrection processing unit 332 then calculates the difference betweenthe average value of the pixel signals of the current target column andthe average value of the pixel signals of the other columns, anddetermines whether or not there is vertical streak noise by determiningwhether or not the difference is larger than a predetermined value. Thevertical streak correction processing unit 332 outputs the determinationresult to the selection unit 333, and, if there is vertical streaknoise, performs correction by replacing each pixel value of the currenttarget column with the average value of the pixel values of the columnsbefore and after the current target column.

The selection unit 333 supplies the selector 334 with a selection signalfor selecting the pixel signal to be selected and output by the selector334, in accordance with a determination result indicating whether or notthere is horizontal streak noise or vertical streak noise. If there ishorizontal streak noise or vertical streak noise, the selection unit 333outputs an error signal from an error pin to the MCU 74.

More specifically, in a case where no correction is required, or wherethe pixel signals in the buffer 330 are to be output without correction,“0” is output to the selector 334. In a case where correction isrequired, “1” is output to the selector 334.

In accordance with the selection signal supplied from the selection unit333, the selector 334 outputs the pixel signals in the buffer 330without correction, or outputs corrected pixel values from a buffer 374of the vertical streak correction processing unit 332.

More specifically, the horizontal streak correction processing unit 331includes a row-by-row average value calculation unit 351, a horizontalstreak threshold determination unit 352, a horizontal streak correctionunit 353, and the buffer 354.

The row-by-row average value calculation unit 351 sets an unprocessedrow in the image stored in the buffer 330 as the current target row,reads the pixel signals of the three rows including the current targetrow and the rows before and after the current target row, calculates theaverage value of each of the three rows, and outputs the average valuesto the horizontal streak threshold determination unit 352.

The horizontal streak threshold determination unit 352 calculates thedifference between the average value of the pixel values of the currenttarget row and the average value of the pixel values of the rows beforeand after the current target row, and compares the difference with apredetermined threshold value. The horizontal streak thresholddetermination unit 352 then determines whether there is horizontalstreak noise, depending on whether or not the difference is larger thanthe predetermined threshold value, and the values of the current targetrow greatly differ from those of the other rows. If the horizontalstreak threshold determination unit 352 determines that there ishorizontal streak noise, the horizontal streak threshold determinationunit 352 outputs information indicating that there is horizontal streaknoise and a failure has been detected to the selection unit 333, andcontrols the horizontal streak correction unit 353 so that thehorizontal streak correction unit 353 calculates a correction value.

Instructed to correct the pixel values of the current target row, thehorizontal streak correction unit 353 performs correction by replacingthe pixel value of each of the pixels of the current target row with theaverage value of the pixel values at each corresponding position in therows before and after the current target row. The horizontal streakcorrection unit 353 then outputs and stores the corrected pixel valuesinto the buffer 354.

More specifically, as shown in a right portion of FIG. 28, in a casewhere horizontal streak noise is detected, the current target row L2 isan abnormal output row formed with abnormal pixel values, and rows L1and L3 before and after the current target row L2 are normal output rowsformed with normal pixel values, for example, the horizontal streakcorrection unit 353 replaces the pixel values of the current target rowL2 with the average value of the respective pixels of the rows L1 andL3.

Meanwhile, the vertical streak correction processing unit 332 includes arow-by-row average value calculation unit 371, a vertical streakthreshold determination unit 372, a vertical streak correction unit 373,and the buffer 374.

The row-by-row average value calculation unit 371 sets an unprocessedcolumn in the image stored in the buffer 354 of the horizontal streakcorrection processing unit 331 as the current target column, reads thepixel signals of the three columns including the current target columnand the columns before and after the current target column, calculatesthe average value of each of the three columns, and outputs the averagevalues to the vertical streak threshold determination unit 372.

The vertical streak threshold determination unit 372 calculates thedifference between the average value of the pixel values of the currenttarget column and the average value of the pixel values of the columnsbefore and after the current target column, and compares the differencewith a predetermined threshold value. The vertical streak thresholddetermination unit 372 then determines whether there is vertical streaknoise, depending on whether or not the difference is larger than thepredetermined threshold value, and the values of the current targetcolumn greatly differ from those of the other columns. If the verticalstreak threshold determination unit 372 determines that there isvertical streak noise, the vertical streak threshold determination unit372 outputs information indicating that there is vertical streak noiseand a failure has been detected to the selection unit 333, and controlsthe vertical streak correction unit 373 so that the vertical streakcorrection unit 373 calculates a correction value.

Instructed to correct the pixel values of the current target column, thevertical streak correction unit 373 performs correction by replacing thepixel value of each of the pixels of the current target column with theaverage value of the pixel values the columns before and after thecurrent target column. The vertical streak correction unit 373 thenoutputs and stores the corrected pixel values into the buffer 374.

More specifically, as shown in a left portion of FIG. 28, in a casewhere vertical streak noise is detected, the current target column R2 isan abnormal output column formed with abnormal pixel values, and columnsR1 and R3 before and after the current target column R2 are normaloutput columns formed with normal pixel values, for example, thevertical streak correction unit 373 replaces the pixel values of thecurrent target column R2 with the average value of the respective pixelsof the columns R1 and R3.

<Correction Process by the Correction Unit in FIG. 27>

Referring now to the flowchart shown in FIGS. 29 and 30, a correctionprocess to be performed by the correction unit 301 shown in FIG. 27 isdescribed.

In step S151, the buffer 330 stores pixel signals supplied from theimage signal output unit 103, and stores the pixel signals as one image.

In step S152, the correction unit 301 initializes counters n and m,which count rows and columns, to 1.

In step S153, the row-by-row average value calculation unit 351 of thehorizontal streak correction processing unit 331 reads the pixel signalsof a total of three rows, or the pixel signals of the nth row as thecurrent target row and the pixel signals of the rows before and afterthe current target row in the image stored in the buffer 330. Therow-by-row average value calculation unit 351 then calculates theaverage value of each of the three rows, and outputs the average valuesto the horizontal streak threshold determination unit 352.

In step S154, the horizontal streak threshold determination unit 352calculates the difference between the average value of the pixel valuesof the nth row as the current target row and the average value of thepixel values of the rows before and after the current target row, andcompares the difference with a predetermined threshold value. Thehorizontal streak threshold determination unit 352 then determineswhether there is horizontal streak noise, depending on whether or notthe difference is larger than the predetermined threshold value, and thepixel values of the current target row greatly differ from the pixelvalues of the other rows.

If the difference between the average value of the pixel values of thenth row as the current target row and the average value of the pixelvalues of the rows before and after the current target row is largerthan the predetermined threshold value, and horizontal streak noise isdetected in step S154, the process moves on to step S155.

In step S155, the horizontal streak threshold determination unit 352outputs information indicating that there is horizontal streak noise anda failure has been detected to the selection unit 333, and instructs thehorizontal streak correction unit 353 to calculate a correction value.Here, the selection unit 333 stores information indicating that thepixel signals of the nth row as the current target row have beencorrected.

In step S156, the horizontal streak correction unit 353 performscorrection by replacing the pixel values of the nth row as the currenttarget row with the average value of the pixel values of the rows beforeand after the current target row, and stores the corrected values intothe buffer 354. The process then moves on to S158.

If it is determined in step S154 that there is no horizontal streaknoise, on the other hand, the process moves on to step S157.

In step S157, a check is made to determine whether or not the counter nis a maximum value N. If the counter n is not the maximum value N, theprocess moves on to step S158.

In step S158, the correction unit 301 increments the counter n by 1, andthe process then returns to step S153.

That is, the process in steps S153 through S158 is repeated to determinewhether or not there is horizontal streak noise. If there is horizontalstreak noise, a process similar to the above described process isrepeated until the process of buffering pixel values corrected with thepreceding and succeeding rows is performed on all the row.

Then, if the process has been performed on all the rows, and it isdetermined in step S157 that the counter n is the maximum value N, theprocess moves on to step S159.

In step S159, the column-by-column average value calculation unit 371 ofthe vertical streak correction processing unit 332 reads the pixelsignals of a total of three columns, or the pixel signals of the mthcolumn as the current target column and the pixel signals of the columnson the right and left sides of the current target column in the imagestored in the buffer 354 of the horizontal streak correction processingunit 331. The column-by-column average value calculation unit 371 thencalculates the average value of each of the three columns, and outputsthe average values to the vertical streak threshold determination unit372.

In step S160, the vertical streak threshold determination unit 372calculates the difference between the average value of the pixel valuesof the current target column and the average value of the pixel valuesof the right and left columns, and compares the difference with apredetermined threshold value. The vertical streak thresholddetermination unit 372 then determines whether there is vertical streaknoise, depending on whether or not the difference is larger than thepredetermined threshold value, and the values of the current targetcolumn greatly differ from those of the other columns.

If the difference between the average value of the pixel values of thecurrent target column and the average value of the pixel values of theright and left columns is larger than the predetermined threshold value,and vertical streak noise is detected in step S160, the process moves onto step S161.

In step S161, the vertical streak threshold determination unit 372outputs information indicating that there is vertical streak noise and afailure has been detected to the selection unit 333, and instructs thevertical streak correction unit 373 to calculate a correction value.Here, the selection unit 333 stores information indicating that thepixel signals of the mth column as the current target column have beencorrected.

In step S162, the vertical streak correction unit 373 performscorrection by replacing the pixel values of the mth column as thecurrent target column with the average value of the pixel values of theright and left columns, and stores the corrected values into the buffer374. The process then moves on to S163.

If it is determined in step S161 that there is no vertical streak noise,on the other hand, the process moves on to step S163.

In step S163, a check is made to determine whether or not the counter mis a maximum value M. If the counter m is not the maximum value M, theprocess moves on to step S164.

In step S164, the correction unit 301 increments the counter m by 1, andthe process then returns to step S159.

That is, the process in steps S159 through S164 is repeated to determinewhether or not there is vertical streak noise. If there is verticalstreak noise, pixel values corrected with the right and left columns arebuffered. If there is no vertical streak noise, a process similar to theabove described process is repeated until the process of buffering thepixel values without any correction is performed on all the columns.

Then, if the process has been performed on all the columns, and it isdetermined in step S163 that the counter m is the maximum value M, theprocess moves on to step S165.

That is, after a horizontal streak correction process is performedthrough the process in steps S153 through S158, a vertical streakcorrection process is performed through the process in steps S159through S164. In this process, a vertical streak correction process isperformed on an image already subjected to a horizontal streakcorrection process. Accordingly, the buffer 374 in the vertical streakcorrection processing unit 332 stores the respective pixels of an imagesubjected to both a vertical streak correction process and a horizontalstreak correction process.

In step S165 (FIG. 30), the selection unit 333 sets an unprocessed pixelas the current target pixel (m, n) among the pixels constituting theimage to be read.

In step S166, the selection unit 333 determines whether or not there isan error in the nth row or the mth column to which the current targetpixel (m, n) belongs, in accordance with correction information. If itis determined in step S166 that there is an error in the current targetpixel (m, n), the process moves on to step S167.

In step S167, the selection unit 333 outputs a signal “1” to theselector 334. The signal “1” is a selection signal for reading the pixelvalue of the corrected current target pixel stored in the buffer 374 ofthe vertical streak correction processing unit 332. In accordance withthe selection signal, the selector 334 reads and outputs the pixel valueof the corrected current target pixel stored in the buffer 374 of thevertical streak correction processing unit 332.

If it is determined in step S166 that there is no error in the currenttarget pixel, on the other hand, the process moves on to step S168.

In step S168, the selection unit 333 outputs a signal “0” to theselector 334. The signal “0” is a selection signal for reading theoriginal pixel value of the uncorrected current target pixel stored inthe buffer 330. In accordance with the selection signal, the selector334 reads and outputs the original pixel value of the uncorrectedcurrent target pixel stored in the buffer 330.

In step S169, the selection unit 333 determines whether or not there isan unprocessed pixel. If there is an unprocessed pixel, the processreturns to step S166. That is, the process in steps S165 through S169 isrepeated until either a corrected pixel value or an original uncorrectedpixel value is selectively read from all the pixels, depending onpresence/absence of an error.

Then, if it is determined in step S169 that there are no moreunprocessed pixels, the process comes to an end.

As the above process is performed, correction can be performed column bycolumn or row by row, even in a case where a failure has occurred in theADCs 242 in a column. Thus, the driving support process can becontinued.

Note that, even when there is a failure in the column ADCs 242, an errorsignal is output from the Error pin. Thus, the MCU 74 can recognizewhich column ADC 242 has a failure, and issue a failure occurrencenotification. However, even if there is a failure in a column ADC 242,and there is a vertical streak error or a horizontal streak error, theimage signal can be corrected, and thus, the driving support process canbe continued. That is, even if there is a vertical streak error or ahorizontal streak error, a process to be performed when a failure hasbeen detected is not performed in step S13 in the flowchart in FIG. 3,but the driving support process can be continued by virtue of theprocess in steps S14 through S17.

Also, in the above described example, the correction unit 301 isprovided in the imaging device 72. However, the correction unit 301 maybe provided in the front camera ECU 73 so that a process similar to theabove can be performed.

Further, in the above described example configuration of the correctionunit 301 shown in FIG. 27, a vertical streak correction process isperformed by the vertical streak correction processing unit 332 after ahorizontal streak correction process is performed by the horizontalstreak correction processing unit 331. However, the process sequence maybe reversed so that a horizontal streak correction process is performedby the horizontal streak correction processing unit 331 after a verticalstreak correction process is performed by the vertical streak correctionprocessing unit 332.

Also, a horizontal streak correction process by the horizontal streakcorrection processing unit 331 and a vertical streak correction processby the vertical streak correction processing unit 332 may be performedin parallel, and the selector 334 may selectively output three kinds ofpixel values, depending on the type of an error that has occurred. Thethree kinds of pixel values are an original pixel value, a pixel valuesubjected to a horizontal streak correction process, and a pixel valuesubjected to a vertical streak correction process. In a case where thesethree kinds of pixel values are selected, of a pixel subjected to both avertical streak correction process and a horizontal streak correctionprocess, the pixel value subjected to the horizontal streak correctionprocess may be selectively output, for example.

4. Fourth Embodiment

In the above described example, a structure in which the imaging device72 and the front camera ECU 73 are designed so that the upper chip 92 asthe first chip and the lower chip 91 as the second chip stacked underthe upper chip 92 are electrically connected by the TCVs 93-1, 93-2,93-11, and 93-12. However, Cu wiring lines may be provided at positionsfacing each other, and the Cu wiring lines may be directly joined toeach other (Cu—Cu junction) so that the upper chip 92 and the lower chip91 are electrically connected.

FIG. 31 shows an example configuration of an imaging device 431 thatincludes a multilayer semiconductor chip 432 in which a firstsemiconductor chip unit 426 having a pixel array 434 formed therein anda second semiconductor chip unit 428 having a logic circuit 455 formedtherein are bonded to each other. Note that the imaging device 431 inFIG. 31 corresponds to the imaging device 72 and the front camera ECU 73described above, the first semiconductor chip unit 426 corresponds tothe upper chip 92, and the second semiconductor chip unit 428corresponds to the lower chip 91.

In the first semiconductor chip unit 426, a semiconductor well region430 is formed in a first semiconductor substrate 433 formed with athinned silicon film. In this semiconductor well region 430, the pixelarray 434 is formed. In the pixel array 434, a plurality of pixels eachincluding a photodiode PD serving as a photoelectric conversion portionand a plurality pixel transistors Tr1 and Tr2 are two-dimensionallyarranged in columns. The photodiodes PD are formed in an effective pixelarray 442 and an optical black region 441 that constitute the pixelarray 434. A plurality of MOS transistors that constitute a controlcircuit (not shown) that controls the pixel array 434 are also formed inthe semiconductor substrate 433. On the side of a front surface 433 a ofthe semiconductor substrate 433, a multilevel wiring layer 437 isformed. In the multilevel wiring layer 437, wiring lines 435 (435 athrough 435 d) and a wiring line 436 that are formed with a plurality of(five in this example) metal layers M1 through M5 are disposed via aninterlayer insulating film 453. Copper (Cu) wiring lines formed by adual damascene technique are used as the wiring lines 435 and 436. Onthe back surface side of the semiconductor substrate 433, a lightblocking film 439 including an upper portion of the optical black region441 is formed via an insulating film 438, and color filters 444 and alens array 445 are formed on the effective pixel array 442 via aplanarizing film 443. The lens array 445 can also be formed on theoptical black region 441.

In the multilevel wiring layer 437 of the first semiconductor chip unit426, the corresponding pixel transistors and the wiring lines 435, andthe adjacent upper and lower wiring lines 435 are connected viaconductive vias 452. Further, the connection wiring line 436 of thefifth metal layer M5 is formed to face the surface 440 joined to thesecond semiconductor chip unit 428. The connection wiring line 436 isconnected to a predetermined wiring line 435 d 1 of the fourth metallayer M4 via conductive vias 452.

In the second semiconductor chip unit 428, a semiconductor well region450 is formed in a second semiconductor substrate 454 including silicon,and the logic circuit 455 serving as a peripheral circuit is formed inthe semiconductor well region 450. The logic circuit 455 is formed witha plurality of MOS transistors Tr11 through Tr14 including CMOStransistors. On the side of the front surface of the secondsemiconductor substrate 454 shown in FIG. 31, a multilevel wiring layer459 is formed. In the multilevel wiring layer 459, wiring lines 457 [457a through 457 c] and a wiring line 458 that are formed with a pluralityof (four in this example) metal layers M11 through M14 are disposed viaan interlayer insulating film 456. Copper (Cu) wiring lines formed by adual damascene technique are used as the wiring lines 457 and 458.

In the multilevel wiring layer 459 of the second semiconductor chip unit428, the MOS transistors Tr11 through Tr14 and the wiring lines 457, andthe adjacent upper and lower wiring lines 457 are connected viaconductive vias 464. Further, the connection wiring line 458 of thefourth metal layer M14 is formed to face the surface 440 joined to thefirst semiconductor chip unit 426. The connection wiring line 458 isconnected to a predetermined wiring line 457 c of the third metal layerM13 via conductive vias 464.

The connection wiring lines 436 and 458 facing the joint surface 440 aredirectly joined to each other so that the multilevel wiring layers 437and 459 face each other. In this manner, the first semiconductor chipunit 426 and the second semiconductor chip unit 428 are electricallyconnected. The direct boning between the connection wiring lines 436 and458 formed with Cu wiring lines is achieved through thermal diffusionbonding. As another method, it is also possible to form a thininsulating film (not shown) on the surfaces of the multilevel wiringlayers 437 and 459, and the multilevel wiring layers 437 and 459 may bejoined by plasma bonding or the like. The direct bonding between theconnection wiring lines 436 and 458 formed with Cu wiring lines forms aCu—Cu junction.

5. Fifth Embodiment

<5-1. First Example Configuration in Which Three Chips Are Stacked>

In the above described example, the imaging device 72 and the frontcamera ECU 73 are formed by stacking two chips formed with the lowerchip 91 and the upper chip 92. However, the imaging device 72 and thefront camera ECU 73 may be formed by stacking a larger number of chips,such as stacking three chips, for example.

FIG. 32 shows an example configuration of the imaging device 72 and thefront camera ECU 73 that are formed by stacking three chips.

FIG. 32 shows a floor plan in which the imaging device 72 and the frontcamera ECU 73 are formed by stacking a first layer chip 501, a secondlayer chip 502, and a third layer chip 503 in this order from the top.The respective floor plans of the first layer chip 501, the second layerchip 502, and the third layer chip 503 are shown in this order from thetop.

A pixel array (Pixel array) 511 is disposed at the center of the firstlayer chip 501, and a row control signal through silicon via (TSV) (TSVfor row driver) 512-12 is disposed along a first side of the pixel array511 (the right side of the pixel array 511 in this embodiment).

Meanwhile, a row drive unit (row decoder) 522 of the second layer chip502 transmits a row control signal for driving pixels to the respectivepixels in each pixel row in the first layer chip 501 via the row controlsignal TSV 512-12. Further, row control signal lines are connected tothe respective pixels in each pixel row, and the row control signallines are connected to the row drive unit 522 of the second layer chip502 via the row control signal TSV 512-12.

Pixel signal TSVs 512-1 and 512-2 for connectingphotoelectrically-converted pixel signals from the respective pixels torespective comparators 541-1 and 541-2 in a plurality ofanalog-to-digital (AD) converters 540-1 and 540-2 disposed in the thirdlayer chip 503 are disposed along second and fourth sides of the pixelarray 511 (the upper and lower sides of the pixel array 511 in thedrawing in this embodiment).

Further, the AD converters 540-1 and 540-2 include the comparators 541-1and 541-2, and counters 542-1 and 542-2, respectively, and convert pixelsignals supplied from the pixel array 511 into digital signals.

Note that the AD converters 540-1 and 540-2 including the comparators541-1 and 541-2 and the counters 542-1 and 542-2 may be disposed in thesecond layer chip 502.

The pixel signal TSVs (TSVs for comparator) 512-1 and 512-2 areconnected to the vertical signal lines of the respective pixels.Further, in a case where a failure detector 521 for the row controlsignal lines is disposed in the second layer chip 502, a TSV (TSV forfailure detector) 512-11 for the failure detector 521 is disposed alonga third side of the pixel array 511 (the left side of the pixel array511 in this embodiment). Note that the TSV (TSV for failure detector)512-11 for the failure detector 521 is preferably disposed on theopposite side of the pixel array 511 from the row control signal lineTSV (TSV for row driver) 512-12.

In the second layer chip 502, a plurality of DRAMs 523 are disposed atthe center, and the row drive unit 522 is disposed along the first sideof the DRAMs 523 (on the right side of the DRAMs 523 in thisembodiment). Further, in a case where the comparators 541-1 and 541-2are disposed in the third layer chip 503, the pixel signal TSVs 512-1and 512-2 for transferring pixel signals are disposed along the secondand fourth sides of the DRAMs 523 (the upper and lower sides of thepixel array 511 in the drawing in this embodiment).

Note that, in a case where the comparators 541-1 and 541-2 of the ADconverters 540-1 and 540-2 are formed in the second layer chip 502, andthe counters 542-1 and 542-2 are formed in the third layer chip 503, thecomparators 541-1 and 541-2 are disposed on the upper and lower sides ofthe DRAMs 523 in the second layer chip 502, and the pixel signal TSVs512-1 and 512-2 for transferring signals from the comparators 541-1 and541-2 to the counters 542-1 and 542-2 in the third layer chip 503 arefurther disposed on the lower side of the plurality of comparators 541-1and 541-2. Further, the failure detector 521 is disposed on the thirdside of the DRAMs 523 (the left side of the DRAMs 523 in the drawing inthis embodiment). The row drive unit 522 is preferably disposed on theopposite side of the DRAMs 523 from the failure detector 521.

In the third layer chip 503, a DRAM control circuit (DRAM Controller)545 for controlling the DRAMs 523 is disposed immediately below theDRAMs 523, and a DRAM control signal TSV (TSV for DRAM) 544 fortransferring control signals from the DRAM control circuit 545 to theDRAMs 523 is disposed. Further, in a case where the comparators 541-1and 541-2 of the AD converters 540-1 and 540-2 are formed in the secondlayer chip 502, and the counters 542-1 and 542-2 are formed in the thirdlayer chip 503, signals from the comparators 541-1 and 541-2 aretransferred to the counters 542-1 and 542-2 via the TSVs 512-1 and512-2.

Also, in a case where there are a plurality of AD converters 540-1 and540-2 in the third layer chip 503, the pixel signal TSVs 512-1 and 512-2of the third layer chip 503 connected to the pixel signal TSVs 512-1 and512-2 of the second layer chip 502 are disposed on the upper side andthe lower side of the AD converters 540-1 and 540-2, respectively.Further, an SRAM memory 543 is disposed on the upper side of the counter542-2 in the drawing. Note that, although FIG. 32 shows a configurationin which a plurality of AD converters 540-1 and 540-2 are provided in anupper portion and a lower portion. However, AD converters may begathered to form one AD converter 540 in an upper portion or a lowerportion in FIG. 32, and the AD converter 540 is designed to read allpixel signals. Further, a failure detector TSV for transferringdetection signals from the failure detector 521 to a signal processingcircuit (not shown) is disposed immediately below the failure detector521.

Note that each of the TSVs 512 for electrically connecting the firstlayer chip 501, the second layer chip 502, and the third layer chip 503described above may be a Cu—Cu junction. In addition, here, the pixelarray 511 corresponds to the pixel array 101, and the TSVs 512correspond to the TCVs 93.

<5-2. Second Example Configuration in Which Three Chips Are Stacked>

In the above described example, the failure detector 521 is provided inthe second layer chip 502. However, the failure detector 521 may beprovided in the third layer chip 503.

FIG. 33 shows an example configuration in which the failure detector 521is provided in the third layer chip 503. Note that, in FIG. 33,components having the same functions as those shown in FIG. 32 aredenoted by the same reference numerals as those in FIG. 32, andexplanation of them will not be repeated as appropriate.

Specifically, in FIG. 33, the failure detector 521 is disposed at theleft end portion of the third layer chip 503 in the drawing. Because ofthis, the failure detector TSV 512-11 is provided on the left side ofthe DRAMs 523 of the second layer chip 503.

<5-3. Third Example Configuration in Which Three Chips Are Stacked>

In the above described example, the row drive unit 522 is provided inthe second layer chip 502. However, the row drive unit 522 may beprovided in the third layer chip 503.

The floor plan in FIG. 34 is an example configuration in which the rowdrive unit 522 of the second layer chip 502 in FIG. 32 is provided inthe third layer chip 503. In this case, the row drive unit 522 in thethird layer chip 503 needs to transmit control signals to the respectivepixels in the pixel array 511. Therefore, instead of the row drive unit522, the row drive unit TSV 512-12 is provided on the right side of theDRAMs 523 in the second layer chip 502.

<5-4. Fourth Example Configuration in Which Three Chips Are Stacked>

In the above described example, the row drive unit 522 is provided inthe third layer chip 503. However, the failure detector 521 may also beprovided in the third layer chip 503.

The floor plan in FIG. 35 is an example configuration in which both therow drive unit 522 and the failure detector 521 of the second layer chip502 in FIG. 32 are provided in the third layer chip 503. In this case,the failure detector 521 and the row drive unit 522 in the third layerchip 503 need to transmit and receive control signals to and from therespective pixels in the pixel array 511. Therefore, instead of thefailure detector 521 and the row drive unit 522, the failure detectorTSV 512-11 and the row drive unit TSV 512-12 are provided on the leftside and the right side of the DRAMs 523, respectively, in the secondlayer chip 502.

<5-5. Fifth Example Configuration in which Three Chips are Stacked>

In the above described example, the DRAMs 523 are provided in the secondlayer chip 502. However, the configuration in the floor plan of thesecond layer chip 502 and the configuration in the floor plan of thethird layer chip 503 shown in FIG. 35 may be replaced with each other,for example.

FIG. 36 shows an example configuration in which the DRAMs 523 in thesecond layer chip 502 shown in FIG. 35 are provided in the third layerchip 503, and the AD converters 540-1 and 540-2, the TSV 544, the DRAMcontrol unit 545, and the DAC 546 in the third layer chip 503 areprovided in the second layer chip 502.

However, as the failure detector 521 and the row drive unit 522 areprovided in the second layer chip 502, the third layer chip 503 does notneed to include the failure detector TSV 512-11 and the row drive unitTSV 512-12.

6. Pixel Signal TSVs

<6-1. Pixel Signal TSVs in a Case Where Comparators and Counters AreDisposed in the Same Chip>

Next, an example configuration of pixel signal TSVs is described.

In the above examples in which three chips are stacked as described withreference to FIGS. 32 through 35, the comparators 541-1 and 541-2 andthe counters 542-1 and 542-2 that constitute the AD converters 540-1 and540-2 are formed in the same third chip 503.

Therefore, pixel signals of the respective pixels in the pixel array 511are transferred from the first chip 501 directly to the third chip 503,without passing through the second chip 502.

In view of this, the pixel signal TSVs 512-1 and 512-2 are designed asshown in FIG. 37, for example.

In FIG. 37, the pixel signal TSVs 512-1 and 512-2 are formed withcontacts by which the first layer chip 501 and the third layer chip 503are electrically connected. The contacts forming the pixel signal TSVs512-1 and 512-2 are connected to contacts of the first layer chip 501and to aluminum pads of the third layer chip 503.

The pixel signals of the pixels constituting the pixel array 511 in thefirst layer chip 501 are transferred to the AD converters 540-1 and540-2 of the third layer chip 503 via the pixel signal TSVs 512-1 and512-2 designed as shown in FIG. 37.

Note that, although the pixel signal TSVs 512-1 and 512-2 have beendescribed above, the failure detector TSV 512-11 and the row drive unitTSV 512-12 may also be designed similarly to the pixel signal TSVs 512-1and 512-2 shown in FIG. 37 in a case where the failure detector 521 andthe row drive unit 522 are provided in the third layer chip 503.

<6-2. Pixel Signal TSVs in a Case Where Comparators And Counters AreDisposed in Different Chips> In the above described example, thecomparators 541-1 and 541-2 and the counters 542-1 and 542-2, whichconstitute the AD converters 540-1 and 540-2, are formed in the samethird layer chip 503. However, the comparators 541-1 and 541-2, and thecounters 542-1 and 542-2 may be formed in different chips.

Specifically, in a case where the comparators 541-1 and 541-2 areprovided in the second layer chip 502, the counters 542-1 and 542-2 areprovided in the third layer chip 503, and the AD converters 540-1 and54-2 are formed, for example, the pixel signals from the respectivepixels in the pixel array 511 formed in the first layer chip 501 areoutput to the comparators 541-1 and 541-2 of the second layer chip 502,and comparison results from the comparators 541-1 and 541-2 aretransferred to the counters 542-1 and 542-2 of the third layer chip 503.

Therefore, as shown in FIG. 38, the pixel signal TSVs 512-1 and 512-2include pixel signal TSVs 512 a-1 and 512 a-2 formed with contacts thatelectrically connect the first layer chip 501 and the second layer chip502, and pixel signal TSVs 512 b-1 and 512 b-2 formed with contacts thatelectrically connect the second layer chip 502 and the third layer chip503, for example.

In such a configuration, the pixel signals from the respective pixels inthe pixel array 511 formed in the first layer chip 501 are output to thecomparators 541-1 and 541-2 of the second layer chip 502 via the pixelsignal TSVs 512 a-1 and 512 a-2. Meanwhile, comparison results from thecomparators 541-1 and 541-2 are transferred to the counters 542-1 and542-2 of the third layer chip 503 via the pixel signal TSVs 512 b-1 and512 b-2.

Note that, although the pixel signal TSVs 512-1 and 512-2 have beendescribed above, the failure detector TSV 512-11 may also be designedsimilarly to the pixel signal TSVs 512-1 and 512-2 shown in FIG. 38 in acase where the failure detector 521 is provided in the second layer chip503.

7. Types of ADCs

<7-1. Column ADC>

Next, types of ADCs are described. Referring to FIG. 39, column ADCsamong the ADCs are first described.

FIG. 39 is a diagram showing an example configuration of an imagingdevice for explaining a column ADC. The imaging device 701 in FIG. 39includes a pixel array unit 711 and a drive unit 712. Further, the driveunit 712 includes a row drive unit 721-1 and a row drive unit 721-2, ananalog-to-digital (AD) conversion unit 722, a test voltage generationunit 723, a reference signal generation unit 724, a control unit 725, asignal processing unit 726, and a failure detector 727.

In the pixel array unit 711, pixels 741 that generate image signalscorresponding to emitted light are arranged in a matrix form. Also, inthe pixel array unit 711, signal lines 713 that transmit control signalsto the pixels 741 are provided for the respective rows, and are sharedamong the pixels 741 disposed in the respective rows. Each signal line713 includes a transfer control signal line for transmitting a transfercontrol signal, a reset control signal line for transmitting a resetcontrol signal, and a pixel selection control signal line forcontrolling the output of image signals from the pixels 741. Also, inthe pixel array unit 711, signal lines 742 for transmitting imagesignals generated by the pixels 741 are provided for the respectivecolumns, and are shared among the pixels 741 disposed in the respectivecolumns.

Further, in the pixel array unit 711, test signal generation units 743that generate a test signal for detecting a failure in the signal lines713 are provided for the respective rows. The test signal generationunits 743 are disposed at both ends of the respective rows, and areprovided with the signal lines 742 and 713, like the pixels 741. Asignal line 714 for transmitting test voltages is further connected tothe test signal generation units 743. Here, the test voltages aresignals for detecting failures in the transfer control signal line andthe reset control signal line described above. The test signalgeneration units 743 generate a transfer test signal and a reset testsignal as test signals. The transfer test signal is generated inaccordance with a test voltage and the transfer control signal, and thereset test signal is generated in accordance with a test voltage and thereset control signal.

The row drive units 721-1 and 721-2 generate control signals for thepixels 741, and output the controls signals via the signal lines 713.The row drive units 721-1 and 721-2 generate the above transfer controlsignal, the above reset control signal, and a pixel selection controlsignal as the control signals. The row drive units 721-1 and 721-2 alsogenerate the same control signals, and simultaneously output the controlsignals to the signal lines 713. This is to provide redundancy in thegeneration of the control signals.

The analog-to-digital conversion unit 722 converts the image signalsgenerated by the pixels 741 into digital image signals. In theanalog-to-digital conversion unit 722, analog-to-digital converters 731that perform analog-to-digital conversion are provided for therespective columns of the pixel array unit 711, and the signal lines 742are connected to the respective analog-to-digital converters 731. Also,in the analog-to-digital conversion unit 722, analog-to-digitalconverters 731 for performing analog-to-digital conversion on the testsignals generated by the test signal generation units 743 or the likeare further provided. The digital image signals generated throughanalog-to-digital conversion are output to the signal processing unit726. Meanwhile, the digital test signals are output to the failuredetector 727.

The test voltage generation unit 723 generates test voltages, andoutputs the test voltages to the test signal generation units 743 viathe signal line 714. The test voltage generation unit 723 generates atransfer test voltage and a reset test voltage as the test voltages. Thetransfer test voltage and the reset test voltage are test voltages withdifferent voltages. The transfer test voltage is a test voltagegenerated when the transfer test signal is generated in the test signalgeneration units 743 or the like, and the reset test voltage is a testvoltage generated when the reset test signal is generated in the testsignal generation units 743 or the like.

The reference signal generation unit 724 generates a reference signal,and outputs the reference signal to the analog-to-digital conversionunit 722. This reference signal is output via a signal line 715. Asignal that has a voltage dropping in a ramp fashion can be used as thereference signal. The reference signal generation unit 724 startsgeneration of the reference signal in synchronization with the start ofanalog-to-digital conversion.

The control unit 725 controls the entire imaging device 701. The controlunit 725 generates a common control signal for controlling the row driveunits 721-1 and 721-2, and outputs the control signal to the row driveunits 721-1 and 721-2 via a signal line 716. The control unit 725 alsogenerates a common control signal for controlling the analog-to-digitalconverters 731 disposed in the analog-to-digital conversion unit 722,and outputs the control signal to all the analog-to-digital converters731 via a signal line 717.

The failure detector 727 detects a failure in the signal lines 713, inaccordance with a failure signal that is output from the test signalgeneration units 743 or the like. The failure detector 727 detects afailure in the transfer test signal line, the reset test signal line,and the pixel selection control signal line, in accordance with thetransfer test signal and the reset test signal. It is possible to detecta failure by comparing a test signal output from the test signalgeneration units 743 or the like with a test signal generated in anormal state. The configuration of the failure detector 727 will bedescribed later in detail.

In the imaging device 701 in the drawing, the pixel array unit 711 andthe drive unit 712 are formed in different semiconductor chips. Thepixel array unit 711 operates with a relatively high power supplyvoltage, to generate image signals. On the other hand, the drive unit712 performs digital signal processing. Therefore, the drive unit 712 isrequired to perform high-speed processing, and is supplied with arelatively low power supply voltage. In this manner, the pixel arrayunit 711 and the drive unit 712 are formed with circuits havingdifferent properties. Therefore, the pixel array unit 711 and the driveunit 712 are separated, and are formed in semiconductor chipsmanufactured through processes suitable for the respective units. Afterthat, these semiconductor chips are bonded to each other, so that theimaging device 701 is formed. In this manner, the cost performance ofthe imaging device 701 can be improved. In this case, the signal lines742, 713, and 714 perform signal transmission between differentsemiconductor chips.

Note that the pixel array unit 711, the row drive units 721-1 and 721-2,the analog-to-digital conversion unit 722, the test voltage generationunit 723, the reference signal generation unit 724, the control unit725, the signal processing unit 726, and the failure detector 727constitute the imaging device 701.

Also, in the example shown FIG. 39, the row drive units 721-1 and 721-2are provided, and two row drive units 721 having the same functions areprovided in the imaging device 701. However, the imaging device 701 mayinclude only one of the row drive units 721.

Further, the signal processing unit 726 processes digital image signalsoutput from the analog-to-digital converters 731. In this process, it ispossible to perform horizontal transfer for sequentially transferringthe digital image signals output from a plurality of analog-to-digitalconverters 731, for example.

In the analog-to-digital conversion unit 722 in the imaging device 701in FIG. 39, a plurality of analog-to-digital converters 731 that performanalog-to-digital conversion are provided for the respective columns ofthe pixel array unit 711, and analog-to-digital conversion is performedon image signals row by row. These analog-to-digital circuits are calledcolumn ADC circuits.

The column ADCs 111 in FIG. 4 of the present disclosure, the imagesignal output unit 103 in FIG. 5, and the ADC 242 in FIG. 18 may beformed with the column ADC circuits described above with reference toFIG. 39. Further, the AD converters 540 in FIG. 32 and FIGS. 35 through38 may be column ADC circuits.

<7-2. Area ADC>

Referring now to FIG. 40, an area ADC is described. FIG. 40 is a diagramshowing an example configuration of an imaging device 701 for explainingan area ADC. Note that, in FIG. 40, components having the same functionsas those of the imaging device 701 shown in FIG. 39 are denoted by thesame reference numerals as those in FIG. 39, and explanation of themwill not be repeated as appropriate. Specifically, the imaging device701 in FIG. 40 differs from the imaging device 701 in FIG. 39 inincluding a plurality of analog-to-digital conversion units 781.

In the pixel array unit 711 of the imaging device 701 in FIG. 40, pixelunits 771, instead of the pixels 741, are arranged in a matrix form.Also, instead of the test signal generation units 743, failure detectionunits 772 are provided for the respective rows. Further, signal lines713 and 714 are connected to the pixel units 771 and the failuredetection units 772, as in the pixel array unit 711 described withreference to FIG. 39.

In the imaging device 701 in FIG. 40, the analog-to-digital conversionunits 781 is provided for the respective pixel units 771 and therespective failure detection units 772 disposed in the pixel array unit711, perform analog-to-digital conversion on image signals or the like,and output each converted image signal or the like to the signalprocessing unit 726 or the failure detector 727. The pixel units 771 andthe failure detection units 772, and the corresponding analog-to-digitalconversion units 781 are individually connected by signal lines 742.

Note that, in the example shown FIG. 40, the row drive units 721-1 and721-2 are provided, and two row drive units 721 having the samefunctions are provided in the imaging device 701. However, the imagingdevice 701 may include only one of the row drive units 721.

Like the analog-to-digital conversion units 781 of the imaging device701 in FIG. 40, analog-to-digital conversion circuits are provided forthe respective pixel units 771 formed with a plurality of pixels in apredetermined area, and perform analog-to-digital conversion on imagesignals area by area. These analog-to-digital conversion circuits arecalled area ADC circuits.

Instead of the column ADCs 111 in FIG. 4, the image signal output unit103 in FIG. 5, and the ADC 242 in FIG. 18 of the present disclosure, thearea ADC circuits described with reference to FIG. 40 may be used.Further, the AD converters 540 in FIG. 32 and FIGS. 35 through 38 may bearea ADC circuits.

Note that, in a case where each of the pixel units 771 is formed withone pixel, the analog-to-digital conversion units 781 are referred toparticularly as pixel ADC circuits. That is, the analog-to-digitalconversion units 781 are formed a pixel-by-pixel basis in this case.

8. Example Structure of WCSP

<8-1. Outline of an Example Structure of WCSP>

FIG. 41 schematically shows an example structure in a case where awafer-level chip size package (WCSP) is adopted as an imaging devicethat is a semiconductor device according to the present technology.

The imaging device 801 shown in FIG. 41 converts light orelectromagnetic waves entering the device from the direction indicatedby an arrow in the drawing, into an electrical signal. In thedescription below in the present disclosure, for ease of explanation,light is the current object to be converted into an electrical signal,and an apparatus that converts light into an electrical signal will bedescribed as an example.

The imaging device 801 includes a stack structure 853 in which a firststructure 851 and a second structure 852 are stacked, external terminals854, and a protective substrate 858 formed on the upper side of thefirst structure 851. Note that, in the description below, the side ofthe incidence surface through which light enters the device will bereferred to as the upper side, and the side of the other surface on theopposite side from the incidence surface will be referred to as thelower side in FIG. 41, for the sake of convenience. In view of this, thefirst structure 851 will be referred to as the upper structure 851, andthe second structure 852 will be referred to as the lower structure 852.

As will be described later, the imaging device 801 is formed in thefollowing manner. A semiconductor substrate (a wafer) forming part ofthe upper structure 851, a semiconductor substrate (a wafer) formingpart of the lower structure 852, and the protective substrate 858 arebonded to one another at the wafer level. The resultant structure isthen divided into individual imaging devices 801.

The upper structure 851 before divided into individual devices is astructure in which pixels for converting incident light into electricalsignals are formed in a semiconductor substrate (a wafer). The pixelseach includes a photodiode (PD) for photoelectric conversion and aplurality of pixel transistors that control photoelectric conversionoperations and operations of reading photoelectrically-convertedelectrical signals, for example. The upper structure 851 included in theimaging device 801 after the division may be referred to as an upperchip, an image sensor substrate, or an image sensor chip in some cases.

The pixel transistors included in the imaging device 801 are preferablyMOS transistors, for example.

On the upper surface of the upper structure 851, color filters 855 ofred (R), green (G), or blue (B) and on-chip lenses 856 are formed, forexample. On the upper side of the on-chip lenses 856, the protectivesubstrate 858 for protecting components in the imaging device 801,particularly the on-chip lenses 856 and the color filters 855, isdisposed. The protective substrate 858 is a transparent glass substrate,for example. Where the hardness of the protective substrate 858 ishigher than the hardness of the on-chip lenses 856, the effect toprotect the on-chip lenses 856 is greater.

The lower structure 852 before the division is a structure in which asemiconductor circuit including transistors and wiring lines is formedin a semiconductor substrate (a wafer). The lower structure 852 includedin the imaging device 801 after the division may be referred to as alower chip, a signal processing substrate, or a signal processing chipin some cases. In the lower structure 852, a plurality of externalterminals 854 for electrically connecting to wiring lines (not shown)outside the device are formed. The external terminals 854 are solderballs, for example.

The imaging device 801 has a cavity-less structure in which theprotective substrate 858 is secured onto the upper side of the upperstructure 851 or the upper side of the on-chip lenses 856 via a glassseal resin 857 provided on the on-chip lenses 856. The hardness of theglass seal resin 857 is lower than the hardness of the protectivesubstrate 858. Accordingly, the stress that is applied from the outsideof the imaging device 801 to the protective substrate 858, andpropagates to the inside of the device can be made lower than in a casewhere there is no seal resin.

Note that the imaging device 801 may have a different structure from thecavity-less structure, or have a cavity structure in which a columnar orwall-like structure is formed on the upper surface of the upperstructure 851, and the protective substrate 858 is secured by the abovecolumnar or wall-like structure so as to be kept with some space leftabove the on-chip lenses 856.

<8-2. Example Circuit Layout in the Imaging Device>

The following is a description of the circuit layout in the imagingdevice 801, or how the respective blocks in the imaging device 801 shownin FIG. 41 are divided into the upper structure 851 and the lowerstructure 852.

FIG. 42 is a diagram showing an example configuration of the circuitlayout in the imaging device 801.

In the example circuit layout, a pixel array unit 864 formed with aplurality of pixels 871 arranged in an array is disposed in the upperstructure 851.

Of the pixel peripheral circuit units included in the imaging device801, part of a row drive unit 862 is disposed in the upper structure851, and part of the row drive unit 862 is disposed in the lowerstructure 852. For example, of the row drive unit 862, a row drivecircuit unit is disposed in the upper structure 851, and a row decoderunit is disposed in the lower structure 852.

The row drive unit 862 disposed in the upper structure 851 is locatedoutside the pixel array unit 864 in the row direction, and at least partof the row drive unit 862 disposed in the lower structure 852 is locatedbelow the row drive unit 862 included in the upper structure 851.

Of the pixel peripheral circuit units included in the imaging device801, part of a column signal processing unit 865 is disposed in theupper structure 851, and part of the column signal processing unit 865is disposed in the lower structure 852. For example, of the columnsignal processing unit 865, a load circuit unit, an amplificationcircuit unit, a noise processing unit, and an ADC comparator unit aredisposed in the upper structure 851, and an ADC counter unit is disposedin the lower structure 852.

The column signal processing unit 865 disposed in the upper structure851 is located outside the pixel array unit 864 in the column direction,and at least part of the column signal processing unit 865 disposed inthe lower structure 852 is located below the column signal processingunit 865 included in the upper structure 851.

Wiring line connection units 869 for connecting the wiring lines of thetwo row drive units 862 are provided on the outer sides of the row driveunit 862 disposed in the upper structure 851 and on the outer sides ofthe row drive unit 862 disposed in the lower structure 852.

Wiring line connection units 869 for connecting the wiring lines of thetwo column signal processing units 865 are also provided on the outersides of the column signal processing unit 865 disposed in the upperstructure 851 and on the outer sides of the column signal processingunit 865 disposed in the lower structure 852. The wiring line connectionstructures that will be described later with reference to FIG. 43 areused In these wiring line connection units 869.

An image signal processing unit 866 is disposed on the inner sides ofthe row drive unit 862 and the column signal processing unit 865disposed in the lower structure 852.

In the lower structure 852, input/output circuit units 889 are disposedin a region located below the pixel array unit 864 in the upperstructure 851.

The input/output circuit units 889 are circuit units each including aninput circuit unit and/or an output circuit unit. In a case where eachinput/output circuit unit 889 is formed with both an input circuit unitand an output circuit unit, a plurality of input/output circuit units889 are provided for the respective external terminals 854, and aredisposed in the lower structure 852. In a case where each input/outputcircuit unit 889 is formed with only an input circuit unit, a pluralityof input circuit units are provided for the respective externalterminals 854 (input terminals), and are disposed in the lower structure852. In a case where each input/output circuit unit 889 is formed withonly an output circuit unit, a plurality of output circuit units areprovided for the respective external terminals 854 (output terminals),and are disposed in the lower structure 852. An image signal processingunit is disposed around the respective input/output circuit units 889divided in plural. In other words, the input/output circuit units 889are disposed in the regions where the image signal processing unit isdisposed.

Note that, in the lower structure 852, the input/output circuit units889 may be disposed in a region below the row drive unit 862 in theupper structure 851 or below the column signal processing unit 865 ofthe upper structure 851.

In other words, the input/output circuit units 889 can be disposed inany appropriate region on the side of the lower structure 852 having theexternal terminals 854 formed thereon, and below the region of the pixelarray unit 864 of the upper structure 851, or below the pixel peripheralcircuit units of the upper structure 851 (the circuit units formed inthe upper structure 851 in the pixel peripheral circuit regions 1013shown in FIG. 4).

<8-3. Cross-Section Structure of the Imaging Device>

A cross-section structure of and the circuit layout in the imagingdevice 801 according to this embodiment are further described, withreference to FIG. 43.

FIG. 43 is a diagram showing a cross-section structure of the imagingdevice 801 taken along the line A-A′ defined in FIG. 42.

At a portion including the upper structure 851 in the imaging device 801and a portion above the upper structure 851, the pixel array unit 864 inwhich a plurality of pixels 871 (FIG. 42) each including an on-chip lens856, a color filter 855, a pixel transistor, and a photodiode 891 arearranged in an array is disposed. In the region of the pixel array unit864 (the pixel array region), pixel transistor regions 1001 are alsoformed. Each pixel transistor region 1001 is a region in which at leastone pixel transistor among a transfer transistor, an amplificationtransistor, and a reset transistor is formed.

A plurality of external terminals 854 are disposed in a region that islocated on the lower surface of a semiconductor substrate 921 includedin the lower structure 852 and is located below the pixel array unit 864included in the upper structure 851.

Note that, in the description with reference to FIG. 43, the “regionthat is located on the lower surface of the semiconductor substrate 921included in the lower structure 852 and is located below the pixel arrayunit 864 included in the upper structure 851” is referred to as a firstspecific region, and the “region that is located on the upper surface ofthe semiconductor substrate 921 included in the lower structure 852 andis located below the pixel array unit 864 included in the upperstructure 851” is referred to as a second specific region.

At least a part of the plurality of external terminals 854 disposed inthe first specific region is a signal input terminal for inputting asignal from the outside to the imaging device 801, or a signal outputterminal 854B for outputting a signal from the imaging device 801 to theoutside. In other words, signal input terminals 854A and signal outputterminals 854B are the external terminals 854 excluding the power supplyterminal and the ground terminal from the external terminals 854. Thesesignal input terminals 854A or signal output terminals 854B are referredto as signal input/output terminals 854C.

Through vias 928 penetrating through the semiconductor substrate 921 aredisposed in the first specific region and in the vicinity of the signalinput/output terminals 854C. Note that a via hole penetrating throughthe semiconductor substrate 921 and a via wiring line formed in the viahole are also collectively referred to as a through via 928.

This through via hole is preferably designed to extend from the lowersurface of the semiconductor substrate 921 to a conductive pad 1022(hereinafter also referred to as a via pad 1022) that is part of amultilevel wiring layer 922 disposed above the upper surface of thesemiconductor substrate 921 and forms the terminal end (the bottomportion) of the via hole.

The signal input/output terminals 854C disposed in the first specificregion are electrically connected to the through vias 928 (morespecifically, the via wiring lines formed in the through via holes) thatare also disposed in the first specific region.

The input/output circuit units 889 including input circuit units oroutput circuit units are disposed in the second specific region and in aregion near the signal input/output terminals 854C and the through vias.

The signal input/output terminals 854C disposed in the first specificregion are electrically connected to the input/output circuit units 889via the through vias 928 and the via pads 1022, or part of themultilevel wiring layer 922.

The regions in which the input/output circuit units 889 are disposed arereferred to as input/output circuit regions 1011. Signal processingcircuit regions 1012 are formed adjacent to the input/output circuitregions 1011 on the upper surface of the semiconductor substrate 921included in the lower structure 852. The signal processing circuitregions 1012 are regions in which the image signal processing unit isformed.

The regions in which pixel peripheral circuit units including all orsome of the row drive units for driving the respective pixels of thepixel array unit 864 and the column signal processing units are arrangedare called pixel peripheral circuit regions 1013. On the lower surfaceof a semiconductor substrate 941 included in the upper structure 861 andon the upper surface of the semiconductor substrate 921 included in thelower structure 852, the pixel peripheral circuit regions 1013 areformed in the regions outside the pixel array unit 864.

The signal input/output terminals 854C may be disposed in regionslocated below the input/output circuit regions 1011 formed in the lowerstructure 852, or may be disposed in regions located below the signalprocessing circuit regions 1012. Alternatively, the signal input/outputterminals 854C may be disposed below the pixel peripheral circuit unitssuch as row drive units or column signal processing units disposed inthe lower structure 852.

The wiring line connection structure for connecting the wiring linesincluded in the multilevel wiring layer 942 of the upper structure 851and the wiring lines included in the multilevel wiring layer 922 of thelower structure 852 is also referred to as an upper-lower wiring lineconnection structure, and the regions in which this structure isdisposed is also referred to as upper-lower wiring line connectionregions 1014.

The upper-lower wiring line connection structure is formed with firstthrough electrodes (silicon through vias) 949 that penetrate through thesemiconductor substrate 941 from the upper surface of the upperstructure 851 to the multilevel wiring layer 942, second throughelectrodes (chip through vias) 945 that penetrate through thesemiconductor substrate 941 and the multilevel wiring layer 942 from theupper surface of the upper structure 851 to the multilevel wiring layer922 of the lower structure 852, and through electrode connection wiringlines 946 for connecting these two kinds of through electrodes (throughsilicon vias: TSVs). Such an upper-lower wiring line connectionstructure is also called a twin contact structure.

The upper-lower wiring line connection regions 1014 are formed outsidethe pixel peripheral circuit regions 1013.

In this embodiment, the pixel peripheral circuit regions 1013 are formedin both the upper structure 851 and the lower structure 852. However,the pixel peripheral circuit regions 1013 may be formed only in one ofthe structures.

Also, the upper-lower wiring line connection regions 1014 are formedoutside the pixel array unit 864 and outside the pixel peripheralcircuit regions 1013. However, the upper-lower wiring line connectionregions 1014 may be formed outside the pixel array unit 864 and insidethe pixel peripheral circuit regions 1013.

Further, a twin contact structure connecting the two kinds of throughelectrodes that are the silicon through vias 949 and the chip throughvias 945 is adopted as the structure that electrically connects themultilevel wiring layer 942 of the upper structure 851 and themultilevel wiring layer 922 of the lower structure 852.

A shared contact structure that connects a wiring layer 943 of the upperstructure 851 and a wiring layer 923 of the lower structure 852 to asingle through electrode may be adopted as a structure that electricallyconnects the multilevel wiring layer 942 of the upper structure 851 andthe multilevel wiring layer 922 of the lower structure 852, for example.

<8-4. Circuit Layout in an Imaging Device in a Case Where a DifferentUpper-Lower Wiring Line Connection Structure Is Used>

The circuit layout and a cross-section structure of the imaging device801 in a case where some other upper-lower wiring line connectionstructure is used are now described, with reference to FIG. 44.

FIG. 44 is a diagram showing a cross-section structure of the imagingdevice 801 taken along the line A-A′ defined in FIG. 42 in a case wherea structure different from the upper-lower wiring line connectionstructure shown in FIG. 42 is used.

In the pixel peripheral circuit regions 1013 in FIG. 44, one of thewiring lines in the multilevel wiring layer 942 of the upper structure851 is disposed in the lowermost plane of the multilevel wiring layer942, or, in other words, in the junction plane between the upperstructure 851 and the lower structure 852. One of the wiring lines inthe multilevel wiring layer 922 of the lower structure 852 is alsodisposed in the uppermost plane of the multilevel wiring layer 922, or,in other words, in the junction plane between the upper structure 851and the lower structure 852. Furthermore, the one of the wiring lines ofthe multilevel wiring layer 942 and the one of the wiring lines of themultilevel wiring layer 922 are disposed at substantially the sameposition in the junction plane, and are electrically connected to eachother. The mode for electrically connecting wiring lines may be a modefor brining two wiring lines into direct contact with each other, or amode in which a thin insulating film or a thin high-resistance film isformed between the two wiring lines, and part of the formed film iselectrically conductive. Alternatively, a thin insulating film or a thinhigh-resistance film may be formed between two wiring lines, and the twowiring lines may transmit an electrical signal through capacitivecoupling.

Where one of the wiring lines of the multilevel wiring layer 942 of theupper structure 851 and one of the wiring lines of the multilevel wiringlayer 922 of the lower structure 852 are formed at substantially thesame position in the above described junction plane, a structure thatelectrically connects the two wiring lines is generally referred to asan upper-lower wiring line direct connection structure or simply as awiring line direct connection structure.

A specific example of the substantially same position is a position atwhich the electrically-connected two wiring lines at least partiallyoverlap each other in a case where the imaging device 801 is viewed fromabove in a plan view, for example. In a case where copper (Cu) is usedas the material of the two connected wiring lines, for example, theconnection structure may be referred to as a Cu—Cu direct junctionstructure or simply as a Cu—Cu junction structure.

In a case where an upper-lower wiring line direct connection structureis used, this connection structure can be disposed outside the pixelarray unit 864. Alternatively, this connection structure can be disposedinside the pixel peripheral circuit region 1013 in the upper structure851 and inside the pixel peripheral circuit region 1013 in the lowerstructure 852. More specifically, among the wiring lines constitutingthe upper-lower wiring line direct connection structure, the wiringlines disposed in the junction plane on the side of the upper structure851 can be disposed below a circuit included in the pixel peripheralcircuit region 1013 in the upper structure 851. Also, among the wiringlines constituting the upper-lower wiring line direct connectionstructure, the wiring lines disposed in the junction plane on the sideof the lower structure 852 can be disposed above a circuit included inthe pixel peripheral circuit region 1013 in the lower structure 852.Alternatively, the wiring lines disposed in the pixel array unit 864(the pixel transistor regions 1001) may be used as the wiring lines ofthe upper structure 851, and an upper-lower wiring line directconnection structure formed with these wiring lines and the wiring linesof the lower structure 852 may be disposed below the pixel array unit864 (the pixel transistor regions 1001).

<8-5. Structure of the Imaging Device in Detail>

Referring now to FIG. 45, the structure of the imaging device 801 isdescribed in detail. FIG. 45 is an enlarged cross-sectional view of aportion in the vicinity of the outer periphery of the imaging device 801having a twin contact structure.

In the lower structure 852, the multilevel wiring layer 922 is formed onthe upper side (the side of the upper structure 851) of thesemiconductor substrate 921 including silicon (Si), for example. Themultilevel wiring layer 922 forms the input/output circuit regions 1011,the signal processing circuit regions 1012 (not shown in FIG. 45), thepixel peripheral circuit regions 1013, and the like, which are shown inFIG. 42.

The multilevel wiring layer 922 includes a plurality of wiring layers923 and an interlayer insulating film 924 formed between the wiringlayers 923. The wiring layers 923 include an uppermost wiring layer 923a closest to the upper structure 851, an intermediate wiring layer 923b, a lowermost wiring layer 923 c closest to the semiconductor substrate921, and the like.

The plurality of wiring layers 923 are formed with copper (Cu), aluminum(Al), tungsten (W), or the like, for example. The interlayer insulatingfilm 924 is formed with a silicon oxide film, a silicon nitride film, orthe like, for example. Each of the plurality of wiring layers 923 andthe interlayer insulating film 924 may be formed with the same materialin all the layers, or may be formed with two or more materials indifferent layers.

At a predetermined position in the semiconductor substrate 921, asilicon through hole 925 penetrating through the semiconductor substrate921 is formed, and a connection conductor 927 is buried in the innerwall of the silicon through hole 925 with an insulating film 926interposed in between, to form a through via (through silicon via: TSV)928. The insulating film 926 may be formed with an SiO2 film, a SiNfilm, or the like, for example. In this embodiment, the through via 928has an inversely tapered shape in which the plane area on the side ofthe wiring layers 923 is smaller than that on the side of the externalterminals 854. However, the through via 928 may have a forward taperedshape in which the plane area on the side of the external terminals 854is smaller, or a non-tapered shape in which the area on the side of theexternal terminals 854 and the area on the side of the wiring layers 923are substantially the same.

The connection conductor 927 of the through via 928 is connected to arewiring line 930 formed on the lower surface side of the semiconductorsubstrate 921, and the rewiring line 930 is connected to the externalterminal 854. The connection conductor 927 and the rewiring line 930 maybe formed with copper (Cu), tungsten (W), titanium (Ti), tantalum (Ta),titanium tungsten alloy (TiW), polysilicon, or the like, for example.

Further, on the lower surface side of the semiconductor substrate 921, asolder mask (solder resist) 931 is formed so as to cover the rewiringline 930 and the insulating film 926, except for the region where theexternal terminal 854 is formed.

Meanwhile, in the upper structure 851, the multilevel wiring layer 942is formed on the lower side (the side of the lower structure 852) of thesemiconductor substrate 941 including silicon (Si), for example. Thecircuits of the pixels 871 are formed with this multilevel wiring layer942.

The multilevel wiring layer 942 includes a plurality of wiring layers943 and an interlayer insulating film 944 formed between the wiringlayers 943. The wiring layers 943 include an uppermost wiring layer 943a closest to the semiconductor substrate 941, an intermediate wiringlayer 943 b, a lowermost wiring layer 943 c closest to the lowerstructure 852, and the like.

The material used for the plurality of wiring layers 943 and theinterlayer insulating film 944 may be the same as the above mentionedmaterial of the wiring layers 923 and the interlayer insulating film924. Also, the plurality of wiring layers 943 and the interlayerinsulating film 944 may be formed with one or more materials, like thewiring layers 923 and the interlayer insulating film 924 describedabove.

Note that, in the example shown in FIG. 45, the multilevel wiring layer942 of the upper structure 851 is formed with five wiring layers 943,and the multilevel wiring layer 922 of the lower structure 852 is formedwith four wiring layers 923. However, the total number of wiring layersis not limited to this, and each multilevel wiring layer can be formedwith any appropriate number of wiring layers.

In the semiconductor substrate 941, photodiodes 891 formed with PNjunctions are formed for the respective pixels 871.

Although not specifically shown in the drawing, a plurality of pixeltransistors such as a transfer transistor and an amplificationtransistor, a floating diffusion (FD), and the like are also formed inthe multilevel wiring layer 942 and the semiconductor substrate 941.

A silicon through via 949 connected to a predetermined wiring layer 943of the upper structure 851, and a chip through via 945 connected to apredetermined wiring layer 923 of the lower structure 852 are formed ata predetermined position in the semiconductor substrate 941 at which thecolor filters 855 and the on-chip lenses 856 are not formed.

The chip through via 945 and the silicon through via 949 are connectedby a connection wiring line 946 formed in the upper surface of thesemiconductor substrate 941. An insulating film 947 is also formedbetween each of the silicon through via 949 and the chip through via 945and the semiconductor substrate 941.

A planarizing film 948 is formed between the photodiodes 891 and thecolor filters 855 in the semiconductor substrate 941, and a planarizingfilm 950 is also formed between the on-chip lenses 856 and the glasssealing resin 857.

As described above, the stack structure 853 of the imaging device 801shown in FIG. 41 is a stack structure in which the multilevel wiringlayer 922 of the lower structure 852 and the multilevel wiring layer 942of the upper structure 851 are joined to each other. In FIG. 45, thejunction plane between the multilevel wiring layer 922 of the lowerstructure 852 and the multilevel wiring layer 942 of the upper structure851 is indicated by a dot-and-dash line.

Further, in the stack structure 853 of the imaging device 801, a wiringlayer 943 of the upper structure 851 and a wiring layer 923 of the lowerstructure 852 are connected by the two through electrodes, the siliconthrough via 949 and the chip through via 945. A wiring layer 923 of thelower structure 852 and an external terminal (back surface electrode)854 are connected by the through via 928 and the rewiring line 930. As aresult, pixel signals generated by the pixels 871 of the upper structure851 are transmitted to the lower structure 852, are subjected to signalprocessing in the lower structure 852, and are output from the externalterminals 854 to the outside of the device.

<8-6. Modifications>

First Modification

Referring now to FIG. 46, a first modification of the imaging device 801is described.

A of FIG. 46 is a cross-sectional view of a portion in the vicinity ofthe outer periphery of the imaging device 801 according to the firstmodification. B of FIG. 46 is a plan view of the imaging device 801 ofthe first modification on the side of the external terminals 854.

In the first modification, as shown in A of FIG. 46, the externalterminals 854 are formed immediately above the through vias 928 so as tooverlap with the positions of the through vias 928 in a plan view.Because of this, the area for forming the rewiring line 930 on the backside of the imaging device 801 becomes unnecessary, as shown in B ofFIG. 46. Thus, a shortage in the area for forming input/output units canbe avoided.

Second Modification

Referring now to FIG. 47, a second modification of the imaging device801 is described.

In the stack structure 853 in the second modification, a wiring layer943 of the lower structure 852 and a wiring layer 923 of the upperstructure 851 are connected by two through electrodes: a silicon throughvia 949 and a chip through via 945. A wiring layer 923 of the upperstructure 851 and a solder ball (back surface electrode) 854 areconnected by a through via (silicon through via) 928 and a rewiring line930. With this arrangement, the plane area of the imaging device 801 canbe minimized.

Further, the portion between the stack structure 853 and the glassprotective substrate 858 is turned into a cavity-less structure, and thestack structure 853 and the protective substrate 858 are bonded to eachother with the glass seal resin 857. Thus, the height can also bereduced.

Accordingly, with the imaging device 801 shown in FIG. 41, a smallersemiconductor device (semiconductor package) can be obtained.

Third Modification

Referring now to FIG. 48, a third modification of the imaging device 801is described.

As shown in FIG. 48, the penetrating vias 928 are not necessarilyrequired, and the penetrating vias 928 may be filled with a solder mask(solder resist) 931, and dicing may be performed at the formationpositions of the through via 928.

The solder mask (solder resist) 931 and the rewiring line 930 areinsulated from each other by an insulating film 926 b. However, as longas the solder mask (solder resist) 931 and the rewiring line 930 areinsulated from each other, a component other than the insulating film926 b may be used, and the glass seal resin 857 may be used for filling,for example.

Also, the glass seal resin 857, the insulating film 926 b, and thesolder mask (solder resist) 931 may all be formed with the samematerial, or some of them may be formed with the same material.

Further, the wiring layer 923 c and the rewiring line 930 areelectrically connected, but the rewiring line 930 may be connected toany wiring layer.

Note that, in the example shown in FIG. 48, a spacer 1112 is providedbetween the stack structure 853 and the glass protective substrate 858so as to form a cavity (a hollow or a space) 1111. However, the spacer1112 is not necessarily provided, and the cavity 1111 may be formed bythe glass seal resin 857. Alternatively, the space of the cavity 1111and the spacer 1112 may be filled with the glass seal resin 857, toobtain a cavity-less structure.

Also, in each imaging device 801 in FIGS. 41 through 48, the upperstructure 851 and the lower structure 852 correspond to the lower chip91 and the upper chip 92 in FIGS. 4 and 5. Accordingly, the imagingdevice 72 and the front camera ECU 73 may be formed with the imagingdevice 801 that is the WCSP described with reference to FIGS. 41 through48.

<8-7. Example of a Three-Layer Stack Structure>

In each of the examples described above, the stack structure 853 of theimaging device 801 is formed with the two layers: the lower structure852 and the upper structure 851. However, the stack structure 853 may beformed with three or more layers.

Referring now to FIGS. 49 and 50, an example of the stack structure 853formed with three layers is described. In this stack structure 853, athird structure 1211 is provided between the lower structure 852 and theupper structure 851.

FIG. 49 shows a configuration in which the pixel array unit 864 has apixel sharing structure.

In the pixel sharing structure, each pixel 871 includes a photodiode(PD) 891 and a transfer transistor 892, but a floating diffusion (FD)893, an amplification transistor 895, a reset transistor 894, and aselection transistor 896 are shared by a plurality of pixels.

FIG. 49 shows a sharing unit 1220 in which the four pixels including twopixels in the row direction and two pixels in the column direction (2×2)share a FD 893, an amplification transistor 895, a reset transistor 894,and a selection transistor 896.

Transfer transistor drive signal lines 1221 extending in the rowdirection are connected to the gate electrodes of four transfertransistors 892 one by one. The four transfer transistor drive signallines 1221 that are connected to the gate electrodes of the fourtransfer transistors 892 and extend in the row direction are arranged inparallel in the column direction.

The FD 893 is connected to the gate electrode of the amplificationtransistor 895 and the diffusion layer of the reset transistor 894 viawiring lines (not shown). A reset transistor drive signal line 1222extending in the row direction is connected to the gate electrode of thereset transistor 894.

A selection transistor drive signal line 1223 extending in the rowdirection is connected to the gate electrode of the selection transistor896. The selection transistor 896 may be omitted in some cases.

The imaging device 801 having the three-layer stack structure 853 shownin FIG. 49 includes an area signal processing unit 1231 in the thirdstructure 1211 between the lower structure 852 and the upper structure851.

The area signal processing unit 1231 includes a read signal processingunit 1232 including a noise processing unit and an ADC, and a dataholding unit 1233 that holes digital data subjected to AD conversion.

For example, in a case where each of the pixels 871 of the sharing unit1220 outputs data represented by 16 bits after AD conversion, the dataholding unit 1233 includes data holding means such as latches and shiftregisters for 64 bits, to hold the data.

The area signal processing unit 1231 further includes an output signalwiring line 1237 for outputting the data held in the data holding unit1233 to the outside of the area signal processing unit 1231. This outputsignal wiring line may be a 64-bit signal line for outputting 64-bitdata held in the data holding unit 1233 in parallel, may be a 16-bitsignal line for outputting the data of four pixels held in the dataholding unit 1233 pixel by pixel, or may be an 8-bit signal line foroutputting half the data of one pixel or a 32-bit signal line foroutputting the data of two pixels, for example. Alternatively, theoutput signal wiring line may be a 1-bit signal line for reading thedata held in the data holding unit 1233 bit by bit.

In the imaging device 801 shown in FIG. 49, one sharing unit 1220 of theupper structure 851 is connected to one area signal processing unit 1231of the third structure 1211. In other words, the sharing units 1220 andthe area signal processing units 1231 have one-to-one correspondence.Therefore, as shown in FIG. 49, the third structure 1211 has an areasignal processing unit array 1234 in which a plurality of area signalprocessing units 1231 are arranged in both the row direction and thecolumn direction.

The third structure 1211 also includes a row address control unit 1235that reads the data in the data holding units 1233 included in therespective area signal processing units 1231 arranged in plural in boththe row direction and the column direction. The row address control unit1235 determines a read position in the row direction, like aconventional semiconductor memory device.

The area signal processing units 1231 arranged in the row direction ofthe area signal processing unit array 1234 are connected to controlsignal lines extending in the row direction from the row address controlunit 1235, and operations of the area signal processing units 1231 arecontrolled by the row address control unit 1235.

The area signal processing units 1231 arranged in the column directionof the area signal processing unit array 1234 are connected to columnread signal lines 1237 extending in the column direction, and the columnread signal lines are connected to a column read unit 1236 disposedahead of the area signal processing unit array 1234.

As for the data held in the data holding units 1233 of the respectivearea signal processing units 1231 of the area signal processing unitarray 1234, the data in the data holding units 1233 of all the areasignal processing units 1231 arranged in the row direction may besimultaneously read out to the column read unit 1236, or only the datain a specific area signal processing unit 1231 designated from thecolumn read unit 1236 may be read out.

A wiring line for outputting data read from the area signal processingunits 1231 to the outside of the third structure 1211 is connected tothe column readout unit 1236.

The lower structure 852 includes a read unit 1241 for receiving dataoutput from the column read unit 1236, with a wiring line from thecolumn read unit 1236 of the third structure 1211 being connected to theread unit 1241.

The lower structure 852 also includes an image signal processing unitfor performing image signal processing on data received from the thirdstructure 1211.

The lower structure 852 further includes an input/output unit foroutputting data received from the third structure 1211 via the imagesignal processing unit or outputting the data not having passed throughthe image signal processing unit. This input/output unit may include notonly an output circuit unit but also an input circuit unit for inputtingthe timing signal to be used in the pixel array unit 864 and thecharacteristic data to be used in the image signal processing unit, forexample, from the outside of the imaging device 801 into the device.

As shown in B of FIG. 50, each sharing unit 1220 formed in the upperstructure 851 is connected to the area signal processing unit 1231 ofthe third structure 1211 disposed immediately below the sharing unit1220. The wiring connection between the upper structure 851 and thethird structure 1211 can be achieved by the Cu—Cu direct junctionstructure shown in FIG. 44, for example.

Also, as shown in B of FIG. 50, the column read unit 1236 outside thearea signal processing unit array 1234 formed in the third structure1211 is connected to the read unit 1241 of the lower structure 852disposed immediately below the column read unit 1236. The wiringconnection between the third structure 1211 and the lower structure 852can be achieved by the Cu—Cu direct junction structure shown in FIG. 44or the twin contact structure shown in FIG. 43, for example.

Accordingly, as shown in A of FIG. 50, pixel signals of the respectivesharing units 1220 formed in the upper structure 851 are output to thecorresponding area signal processing units 1231 of the third structure1211. The data held in the data holding units 1233 of the area signalprocessing units 1231 is output from the column reading unit 1236, andis supplied to the read unit 1241 of the lower structure 852. In theimage signal processing unit, various kinds of signal processing (a tonecurve correction process, for example) are then performed on the data,and the resultant data is output from the input/output unit to theoutside of the device.

Note that, in the imaging device 801 with the three-layer stackstructure 853, the input/output unit formed in the lower structure 852may be disposed below the row address control unit 1235 of the thirdstructure 1211.

Also, in the imaging device 801 with the three-layer stack structure853, the input/output unit formed in the lower structure 852 may bedisposed below the area signal processing units 1231 of the thirdstructure 1211.

Further, in the imaging device 801 with the three-layer stack structure853, the input/output unit formed in the lower structure 852 may bedisposed below the pixel array unit 864 of the upper structure 851.

Note that the imaging device 801 having the three-layer stack structure853 formed with the lower structure 852, the upper structure 851, andthe third structure 1211 shown in FIGS. 49 and 50 corresponds to thefirst through third layer chips 501 through 503 shown in FIGS. 32through 35. Accordingly, the imaging device 72 and the front camera ECU73 with the three stacked chips shown in FIGS. 32 through 35 may beformed with the imaging device 801 that is a WCSP formed with thethree-layer stack structure 853 described above with reference to FIGS.49 and 50.

Note that the above embodiments can be appropriately combined.Specifically, the Cu—Cu junction described with reference to the fourthembodiment can also be applied to the TSVs 512 in another embodimentsuch as the floor plan of the fifth embodiment in which three chips arestacked, for example.

9. Example Application to an Electronic Apparatus

The above described imaging device 72 and front camera ECU 73 shown inFIGS. 5 and 18, or the imaging device 72 that includes some of thefunctions of the front camera ECU 73 and is capable of failure detectionindependently can be used in various kinds of electronic apparatuses,such as imaging apparatuses like digital still cameras and digital videocameras, portable telephone devices having imaging functions, and otherapparatuses having imaging functions, for example.

FIG. 51 is a block diagram showing an example configuration of animaging apparatus as an electronic apparatus to which the presenttechnology is applied.

The imaging apparatus 2001 shown in FIG. 51 includes an optical system2002, a shutter device 2003, a solid-state imaging device 2004, acontrol circuit 2005, a signal processing circuit 2006, a monitor 2007,and a memory 2008, and can take still images and moving images.

The optical system 2002 includes one or more lenses to guide light(incident light) from an object to the solid-state imaging device 2004,and form an image on the light receiving surface of the solid-stateimaging device 2004.

The shutter device 2003 is placed between the optical system 2002 andthe solid-state imaging device 2004, and, under the control of thecontrol circuit 2005, controls the light emission period and the lightblocking period for the solid-state imaging device 2004.

The solid-state imaging device 2004 is formed with a package containingthe above described solid-state imaging device. In accordance with lightthat is emitted to form an image on the light receiving surface via theoptical system 2002 and the shutter device 2003, the solid-state imagingdevice 2004 accumulates signal charges for a certain period of time. Thesignal charges accumulated in the solid-state imaging device 2004 aretransferred in accordance with a drive signal (timing signal) suppliedfrom the control circuit 2005.

The control circuit 2005 outputs the drive signal that controls thetransfer operation of the solid-state imaging device 2004 and theshutter operation of the shutter device 2003, to drive the solid-stateimaging device 2004 and the shutter device 2003.

The signal processing circuit 2006 performs various kinds of signalprocessing on signal charges that are output from the solid-stateimaging device 2004. The image (image data) obtained through the signalprocessing performed by the signal processing circuit 2006 is suppliedto and displayed on the monitor 2007, or is supplied to and stored(recorded) into the memory 2008.

In the imaging apparatus 2001 designed as above, the imaging device 72and the front camera ECU 73 shown in FIGS. 5 and 18 can also be used inplace of the above described solid-state imaging device 2004 and signalprocessing circuit 2006, or the imaging device 72 that includes some ofthe functions of the front camera ECU 73 and is capable of failuredetection independently can also be used in place of the solid-stateimaging device 2004. Thus, the imaging apparatus 2001 becomes capable offailure detection independently.

10. Examples of Use of the Imaging Device

FIG. 52 is a diagram showing examples of use of the imaging device 72and the front camera ECU 73 shown in FIGS. 5 and 18, or the imagingdevice 72 that includes some of the functions of the front camera ECU 73and is capable of failure detection independently.

The above described camera module can be used in various cases wherelight such as visible light, infrared light, ultraviolet light, or anX-ray is sensed, as described below, for example.

Devices configured to take images for appreciation activities, such asdigital cameras and portable devices with camera functions.

Devices for transportation use, such as vehicle-mounted sensorsconfigured to take images of the front, the back, the surroundings, theinside, and the like of an automobile to perform safe driving like anautomatic stop, recognize a driver's condition and the like,surveillance cameras for monitoring running vehicles and roads, andranging sensors for measuring distances between vehicles or the like.

Devices to be used in conjunction with home electric appliances, such astelevision sets, refrigerators, and air conditioners, to take images ofgestures of users and operate the appliances in accordance with thegestures.

Devices for medical care use and health care use, such as endoscopes anddevices for receiving infrared light for angiography.

Devices for security use, such as surveillance cameras for crimeprevention and cameras for personal authentication.

Devices for beauty care use, such as skin measurement devices configuredto image the skin and microscopes for imaging the scalp.

Devices for sporting use, such as action cameras and wearable camerasfor sports or the like.

Devices for agricultural use such as cameras for monitoring conditionsof fields and crops.

11. Example Applications to Moving Objects

The technology according to the present disclosure (the presenttechnology) can be applied to various products. For example, thetechnology according to the present disclosure may be embodied as anapparatus mounted on any type of moving object, such as an automobile,an electrical vehicle, a hybrid electrical vehicle, a motorcycle, abicycle, a personal mobility device, an airplane, a drone, a vessel, ora robot.

FIG. 53 is a block diagram schematically showing an exampleconfiguration of a vehicle control system that is an example of a movingobject control system to which the technology according to the presentdisclosure can be applied.

The vehicle control system 12000 includes a plurality of electroniccontrol units connected via a communication network 12001. In theexample shown in FIG. 53, the vehicle control system 12000 includes adrive system control unit 12010, a body system control unit 12020, anexternal information detection unit 12030, an in-vehicle informationdetection unit 12040, and an overall control unit 12050. A microcomputer12051, a sound/image output unit 12052, and an in-vehicle networkinterface (I/F) 12053 are also shown as the functional components of theoverall control unit 12050.

The drive system control unit 12010 controls operations of the devicesrelated to the drive system of the vehicle according to variousprograms. For example, the drive system control unit 12010 functions ascontrol devices such as a driving force generation device for generatinga driving force of the vehicle such as an internal combustion engine ora driving motor, a driving force transmission mechanism for transmittingthe driving force to the wheels, a steering mechanism for adjusting thesteering angle of the vehicle, and a braking device for generating abraking force of the vehicle.

The body system control unit 12020 controls operations of the variousdevices mounted on the vehicle body according to various programs. Forexample, the body system control unit 12020 functions as a keyless entrysystem, a smart key system, a power window device, or a control devicefor various lamps such as a headlamp, a backup lamp, a brake lamp, aturn signal lamp, and a fog lamp. In this case, the body system controlunit 12020 can receive radio waves transmitted from a portable devicethat substitutes for a key, or signals from various switches. The bodysystem control unit 12020 receives inputs of these radio waves orsignals, and controls the door lock device, the power window device, thelamps, and the like of the vehicle.

The external information detection unit 12030 detects informationoutside the vehicle equipped with the vehicle control system 12000. Forexample, an imaging unit 12031 is connected to the external informationdetection unit 12030. The external information detection unit 12030causes the imaging unit 12031 to capture an image of the outside of thevehicle, and receives the captured image. In accordance with thereceived image, the external information detection unit 12030 mayperform an object detection process for detecting a person, a vehicle,an obstacle, a sign, characters on the road surface, or the like, orperform a distance detection process.

The imaging unit 12031 is an optical sensor that receives light, andoutputs an electrical signal corresponding to the amount of receivedlight. The imaging unit 12031 can output an electrical signal as animage, or output an electrical signal as distance measurementinformation. Further, the light to be received by the imaging unit 12031may be visible light, or may be invisible light such as infrared light.

The in-vehicle information detection unit 12040 detects informationabout the inside of the vehicle. For example, a driver state detector12041 that detects the state of the driver is connected to thein-vehicle information detection unit 12040. The driver state detector12041 includes a camera that captures an image of the driver, forexample, and, in accordance with detected information input from thedriver state detector 12041, the in-vehicle information detection unit12040 may calculate the degree of fatigue or the degree of concentrationof the driver, or determine whether the driver is dozing off.

In accordance with the external/internal information acquired by theexternal information detection unit 12030 or the in-vehicle informationdetection unit 12040, the microcomputer 12051 can calculate the controltarget value of the driving force generation device, the steeringmechanism, or the braking device, and output a control command to thedrive system control unit 12010. For example, the microcomputer 12051can perform cooperative control to achieve the functions of an advanceddriver assistance system (ADAS), including vehicle collision avoidanceor impact mitigation, follow-up running based on the distance betweenvehicles, vehicle speed maintenance running, vehicle collision warning,vehicle lane deviation warning, or the like.

The microcomputer 12051 can also perform cooperative control to conductautomatic driving or the like for autonomously running not depending onthe operation of the driver, by controlling the driving force generationdevice, the steering mechanism, the braking device, or the like inaccordance with information about the surroundings of the vehicle, theinformation having being acquired by the external information detectionunit 12030 or the in-vehicle information detection unit 12040.

The microcomputer 12051 can also output a control command to the bodysystem control unit 12020, in accordance with the external informationacquired by the external information detection unit 12030. For example,the microcomputer 12051 controls the headlamp in accordance with theposition of the leading vehicle or the oncoming vehicle detected by theexternal information detection unit 12030, and performs cooperativecontrol to achieve an anti-glare effect by switching from a high beam toa low beam, or the like.

The sound/image output unit 12052 transmits an audio output signaland/or an image output signal to an output device that is capable ofvisually or audibly notifying the passenger(s) of the vehicle or theoutside of the vehicle of information. In the example shown in FIG. 53,an audio speaker 12061, a display unit 12062, and an instrument panel12063 are shown as output devices. The display unit 12062 may include anon-board display and/or a head-up display, for example.

FIG. 54 is a diagram showing an example of the installation position ofthe imaging unit 12031.

In FIG. 54, imaging units 12101, 12102, 12103, 12104, and 12105 areincluded as the imaging unit 12031.

Imaging units 12101, 12102, 12103, 12104, and 12105 are provided at thefollowing positions: the front end edge of a vehicle 12100, a sidemirror, the rear bumper, a rear door, an upper portion of the frontwindshield inside the vehicle, and the like, for example. The imagingunit 12101 provided on the front end edge and the imaging unit 12105provided on the upper portion of the front windshield inside the vehiclemainly capture images ahead of the vehicle 12100. The imaging units12102 and 12103 provided on the side mirrors mainly capture images onthe sides of the vehicle 12100. The imaging unit 12104 provided on therear bumper or a rear door mainly captures images behind the vehicle12100. The imaging unit 12105 provided on the upper portion of the frontwindshield inside the vehicle is mainly used for detection of a vehiclerunning in front of the vehicle, a pedestrian, an obstacle, a trafficsignal, a traffic sign, a lane, or the like.

Note that FIG. 54 shows an example of the imaging ranges of the imagingunits 12101 through 12104. An imaging range 12111 indicates the imagingrange of the imaging unit 12101 provided on the front end edge, imagingranges 12112 and 12113 indicate the imaging ranges of the imaging units12102 and 12103 provided on the respective side mirrors, and an imagingrange 12114 indicates the imaging range of the imaging unit 12104provided on the rear bumper or a rear door. For example, image datacaptured by the imaging units 12101 through 12104 are superimposed onone another, so that an overhead image of the vehicle 12100 viewed fromabove is obtained.

At least one of the imaging units 12101 through 12104 may have afunction of acquiring distance information. For example, at least one ofthe imaging units 12101 through 12104 may be a stereo camera including aplurality of imaging devices, or may be an imaging device having pixelsfor phase difference detection.

For example, in accordance with distance information obtained from theimaging units 12101 through 12104, the microcomputer 12051 calculatesthe distances to the respective three-dimensional objects within theimaging ranges 12111 through 12114, and temporal changes in thedistances (the speeds relative to the vehicle 12100). In this manner,the three-dimensional object that is the closest three-dimensionalobject on the traveling path of the vehicle 12100 and is traveling at apredetermined speed (0 km/h or higher, for example) in substantially thesame direction as the vehicle 12100 can be extracted as the vehiclerunning in front of the vehicle 12100. Further, the microcomputer 12051can set beforehand an inter-vehicle distance to be maintained in frontof the vehicle running in front of the vehicle 12100, and can performautomatic brake control (including follow-up stop control), automaticacceleration control (including follow-up start control), and the like.In this manner, it is possible to perform cooperative control to conductautomatic driving or the like to autonomously travel not depending onthe operation of the driver.

For example, in accordance with the distance information obtained fromthe imaging units 12101 through 12104, the microcomputer 12051 canextract three-dimensional object data concerning three-dimensionalobjects under the categories of two-wheeled vehicles, regular vehicles,large vehicles, pedestrians, utility poles, and the like, and use thethree-dimensional object data in automatically avoiding obstacles. Forexample, the microcomputer 12051 classifies the obstacles in thevicinity of the vehicle 12100 into obstacles visible to the driver ofthe vehicle 12100 and obstacles difficult to visually recognize. Themicrocomputer 12051 then determines collision risks indicating the risksof collision with the respective obstacles. If a collision risk is equalto or higher than a set value, and there is a possibility of collision,the microcomputer 12051 outputs a warning to the driver via the audiospeaker 12061 and the display unit 12062, or can perform driving supportfor avoiding collision by performing forced deceleration or avoidingsteering via the drive system control unit 12010.

At least one of the imaging units 12101 through 12104 may be an infraredcamera that detects infrared light. For example, the microcomputer 12051can recognize a pedestrian by determining whether or not a pedestrianexists in images captured by the imaging units 12101 through 12104. Suchpedestrian recognition is carried out through a process of extractingfeature points from the images captured by the imaging units 12101through 12104 serving as infrared cameras, and a process of performing apattern matching on the series of feature points indicating the outlinesof objects and determining whether or not there is a pedestrian, forexample. If the microcomputer 12051 determines that a pedestrian existsin the images captured by the imaging units 12101 through 12104, andrecognizes a pedestrian, the sound/image output unit 12052 controls thedisplay unit 12062 to display a rectangular contour line for emphasizingthe recognized pedestrian in a superimposed manner. The sound/imageoutput unit 12052 may also control the display unit 12062 to display anicon or the like indicating the pedestrian at a desired position.

An example of a vehicle control system to which the technique accordingto the present disclosure can be applied has been described above. Thetechnique according to the present disclosure can be applied to theimaging unit 12031 and the external information detection unit 12030 inthe above described configuration. Specifically, the imaging device 72and the front camera ECU 73 shown in FIGS. 5 and 18, or the imagingdevice 72 that includes some of the functions of the front camera ECU 73and is capable of failure detection independently can be used as theimaging unit 12031 and the external information detection unit 12030. Asthe technology according to the present disclosure is applied to theimaging unit 12031 and the external information detection unit 12030, itbecomes possible to detect a failure. Accordingly, it becomes possibleto stop driving support based on information from the imaging unit 12031having a failure therein or the external information detection unit12030 having a failure therein. Thus, it becomes possible to avoid adangerous situation caused by wrong driving support based on wronginformation.

It should be noted that the present disclosure may also be embodied inthe configurations described below.

<1> An imaging apparatus including:

a first substrate including a pixel and a pixel control line; and

a second substrate, the first substrate and the second substrate beingstacked on each other, in which

the second substrate includes a row drive unit and a failure detector,

one end of the pixel control line is connected to the row drive unit viaa first connection electrode,

the other end of the pixel control line is connected to the failuredetector via a second connection electrode,

the row drive unit supplies a control signal for controlling operationof the pixel to the pixel control line via the first connectionelectrode, and

the failure detector detects a failure in accordance with the controlsignal supplied via the first connection electrode, the pixel controlline, and the second connection electrode.

<2> The imaging apparatus according to <1>, in which

the first connection electrode and the second connection electrode areformed with through electrodes penetrating through the first substrateand the second substrate, and

the first substrate and the second substrate are stacked and areelectrically connected by the through electrodes.

<3> The imaging apparatus according to <1> or <2>, in which

the pixels are arranged in an array,

the imaging apparatus further includes a control unit that outputsaddress information about a current target among the pixels andinformation about timing at which the pixel specified by the addressinformation is controlled, and

the failure detector includes:

a detector that detects the control signal for controlling operation ofthe pixel and outputs a detection signal, the control signal beingsupplied from the row drive unit specified by the address informationoutput from the control unit; and

a pulse output failure detector that detects a failure in a pulse outputof the control signal, depending on whether or not the detection signalis output when the control signal for controlling operation of the pixelspecified by the address information output from the control unit isdetected by the detector at the timing at which the pixel specified bythe address information is controlled.

<4> The imaging apparatus according to <3>, in which

the detector

includes a switching gate that detects the control signal forcontrolling operation of the pixel, the switching gate being specifiedby the address information output from the control unit, and

supplies electric power only to the switching gate specified by theaddress information output from the control unit,

when having detected the control signal for controlling operation of thepixel, the switching gate outputs a Hi signal to a bus set for eachcorresponding control signal, and

the pulse output failure detector

includes a plurality of holding units that hold a value for each controlsignal, the value depending on a signal output to the bus set for eachcontrol signal and a signal indicating the timing at which the pixelspecified by the address information is controlled, and

detects a failure in a pulse output of the control signal, in accordancewith the value held by the holding units.

<5> The imaging apparatus according to <4>, in which

the plurality of holding units hold a value for each control signal, thevalue depending on a signal output to the bus set for each controlsignal and a fixed signal indicating that the pixel specified by theaddress information is in a controlled state, and

the pulse output failure detector detects a failure in a pulse output ofthe control signal, in accordance with the value held by the holdingunits.

<6> The imaging apparatus according to <3>, in which the row drive unitand the first substrate are connected by the first connection electrodeformed with a through electrode, and the detector and the firstsubstrate are electrically connected by the second connection electrodeformed with another through electrode different from the throughelectrode.

<7> The imaging apparatus according to <3>, in which

the control unit outputs the address information about the currenttarget among the pixels to the row drive unit and the detector,

the row drive unit outputs selection information about an address of therow drive unit, the selection information corresponding to the addressinformation,

the detector outputs selection information about an address of thedetector, the selection information corresponding to the addressinformation,

the failure detector includes an address select function failuredetector that compares the selection information about the address ofthe row drive unit and the selection information about the address ofthe detector with the address information output from the control unit,and, in accordance with a result of the comparison, detects a failure inan address select function in the row drive unit and the detector.

<8> An imaging method implemented in an imaging apparatus including:

a first substrate including a pixel and a pixel control line; and

a second substrate, the first substrate and the second substrate beingstacked on each other,

the second substrate including a row drive unit and a failure detector,

one end of the pixel control line being connected to the row drive unitvia a first connection electrode,

the other end of the pixel control line being connected to the failuredetector via a second connection electrode,

the imaging method including the steps of:

the row drive unit supplying a control signal for controlling operationof the pixel to the pixel control line via the first connectionelectrode; and

the failure detector detecting a failure in accordance with the controlsignal supplied via the first connection electrode, the pixel controlline, and the second connection electrode.

<9> A camera module including:

a first substrate including a pixel and a pixel control line; and

a second substrate, the first substrate and the second substrate beingstacked on each other, in which

the second substrate includes a row drive unit and a failure detector,

one end of the pixel control line is connected to the row drive unit viaa first connection electrode,

the other end of the pixel control line is connected to the failuredetector via a second connection electrode,

the row drive unit supplies a control signal for controlling operationof the pixel to the pixel control line via the first connectionelectrode, and

the failure detector detects a failure in accordance with the controlsignal supplied via the first connection electrode, the pixel controlline, and the second connection electrode.

<10> An electronic apparatus including:

a first substrate including a pixel and a pixel control line; and

a second substrate, the first substrate and the second substrate beingstacked on each other, in which

the second substrate includes a row drive unit and a failure detector,

one end of the pixel control line is connected to the row drive unit viaa first connection electrode,

the other end of the pixel control line is connected to the failuredetector via a second connection electrode,

the row drive unit supplies a control signal for controlling operationof the pixel to the pixel control line via the first connectionelectrode, and

the failure detector detects a failure in accordance with the controlsignal supplied via the first connection electrode, the pixel controlline, and the second connection electrode.

<11> An imaging apparatus including:

a first substrate including a pixel and a vertical signal line connectedto the pixel; and

a second substrate, the first substrate and the second substrate beingstacked on each other, in which

the second substrate includes a signal supply circuit, ananalog-to-digital conversion circuit, and a failure detector,

one end of the vertical signal line is connected to the signal supplycircuit via a first connection electrode,

the other end of the vertical signal line is connected to theanalog-to-digital conversion circuit via a second connection electrode,

the signal supply circuit supplies a dummy pixel signal to the verticalsignal line via the first connection electrode,

the analog-to-digital conversion circuit outputs a digital signal inaccordance with the dummy pixel signal, and

the failure detector detects a failure in accordance with the digitalsignal.

<12> An imaging apparatus including:

a first substrate on which a pixel is mounted; and

a second substrate on which a signal processing unit that performssignal processing on an image captured by the pixel is mounted, in which

the first substrate and the second substrate are stacked and areelectrically connected, and

the signal processing unit detects a failure through the signalprocessing.

REFERENCE SIGNS LIST

11 Vehicle

31 ECU

32 Front camera module

33 Steering wheel

34 Headlamp

35 Motor

36 Engine

37 Brake

38 Display unit

71 Lens

72 Imaging device

73 Front camera ECU

74 MCU

91 Lower chip

92 Upper chip

93, 93-1, 93-2, 93-11, 93-12 TCV

101 Pixel array

102 Row drive unit

103 Image signal output unit

121 Control unit

122 Image processing unit

123 Output unit

124 Failure detector

141 Row address selecting function failure detector

142 Pulse output failure detector

143 Control line gate

161 Address decoder

162 Shutter address latch

163 Read address latch

164 to 168 Switching gate

169, 170 Inverter

181 Failure determination unit

182 to 186 Latch

191 to 195 Latch

201 Failure detection column

202 Pixel control line failure detector

230 Photodiode

231 Transfer transistor

232 Reset transistor

233 FD

234 Amplification transistor

235 Selection transistor

241 Load MOS

242 ADC

243 Horizontal transfer unit

250 DSF circuit

251 Switch transistor

252 DSF transistor

261 Comparator

262 Counter

263 DAC

271 ADC+TCV failure detector

The invention claimed is:
 1. A light detecting device comprising: apixel array including a first pixel configured to output a first analogsignal; a first circuit configured to output a second analog signal; afirst column signal line coupled to the first pixel and the firstcircuit; a first plurality of connectors disposed outside the pixelarray and along a first side edge of the pixel array; a firstanalog-to-digital converter coupled to the first column signal line viaa first connector of the first plurality of connectors, the firstanalog-to-digital converter configured to output a first digital signalbased on the first analog signal and to output a second digital signalbased on the second analog signal; a failure detector coupled to thefirst analog-to-digital converter, the failure detector configured toperform failure detection of a signal path including the first columnsignal line, the first connector and the first analog-to-digitalconverter based on the second digital signal, wherein the pixel array isdisposed in a first substrate and the first analog-to-digital converteris disposed in a second substrate that is stacked with the firstsubstrate via the first plurality of connectors.
 2. The light detectingdevice according to claim 1, wherein the first pixel includes aphotodiode and first pixel transistors.
 3. The light detecting deviceaccording to claim 2, wherein the first circuit does not include aphotodiode.
 4. The light detecting device according to claim 1, whereinthe first circuit includes a first nMOS transistor.
 5. The lightdetecting device according to claim 1, wherein the first connector is athrough silicon via.
 6. The light detecting device according to claim 1,further comprising a pixel control circuit in the second substrate. 7.The light detecting device according to claim 6, wherein the pixelcontrol circuit is coupled to the first pixel via a second connector ofa second plurality of connectors, the second plurality of connectorsbeing disposed outside the pixel array and along a second side edge ofthe pixel array.
 8. The light detecting device according to claim 7,wherein the second side edge is perpendicular to the first side edge. 9.The light detecting device according to claim 1, wherein the failuredetection is performed in a blanking period.
 10. The light detectingdevice according to claim 1, wherein the first digital signal isoutputted as a pixel signal.
 11. The light detecting device according toclaim 1, wherein the failure detector is disposed in a second substrate.12. The light detecting device according to claim 1, wherein the firstcircuit is disposed in the second substrate.
 13. A light detectingsensor comprising: a pixel array including a first pixel configured tooutput a first analog signal; a first circuit configured to output asecond analog signal; a first column signal line coupled to the firstpixel and the first circuit; a first plurality of connectors disposedoutside the pixel array and along a first side edge of the pixel array;a first analog-to-digital converter coupled to the first column signalline via a first connector of the first plurality of connectors, thefirst analog-to-digital converter configured to output a first digitalsignal based on the first analog signal and to output a second digitalsignal based on the second analog signal; a failure detector configuredto perform failure detection of a signal path including the first columnsignal line and the first connector based on the second analog signal,wherein the pixel array is disposed in a first substrate and the firstanalog-to-digital converter is disposed in a second substrate that isstacked with the first substrate via the first plurality of connectors.14. The light detecting sensor according to claim 13, wherein the firstpixel includes a photodiode and first pixel transistors.
 15. The lightdetecting sensor according to claim 14, wherein the first circuit doesnot include a photodiode.
 16. The light detecting sensor according toclaim 13, wherein the first circuit includes a first nMOS transistor.17. The light detecting sensor according to claim 13, wherein the firstconnector is a through silicon via.
 18. The light detecting sensoraccording to claim 13, further comprising a pixel control circuit in thesecond substrate.
 19. The light detecting sensor according to claim 18,wherein the pixel control circuit is coupled to the first pixel via asecond connector of a second plurality of connectors, the secondplurality of connectors being disposed outside the pixel array and alonga second side edge of the pixel array.
 20. The light detecting sensoraccording to claim 19, wherein the second side edge is perpendicular tothe first side edge.
 21. The light detecting sensor according to claim12, wherein the failure detection is performed in a blanking period. 22.The light detecting sensor according to claim 12, wherein the firstdigital signal is outputted as a pixel signal.
 23. The light detectingsensor according to claim 12, wherein the failure detector is disposedin a second substrate.
 24. The light detecting sensor according to claim12, wherein the first circuit is disposed in the second substrate.
 25. Avehicle control system comprising: an imaging unit configured to capturean image of an outside of a vehicle and to output the image, the imagingunit including: a pixel array including a first pixel configured tooutput a first analog signal; a first circuit configured to output asecond analog signal; a first column signal line coupled to the firstpixel and the first circuit; a first plurality of connectors disposedoutside the pixel array and along a first side edge of the pixel array;a first analog-to-digital converter coupled to the first column signalline via a first connector of the first plurality of connectors, thefirst analog-to-digital converter configured to output a first digitalsignal based on the first analog signal and to output a second digitalsignal based on the second analog signal; and a failure detectorconfigured to perform failure detection of a signal path including thefirst column signal line and the first connector based on the secondanalog signal, wherein the pixel array is disposed in a first substrateand the first analog-to-digital converter is disposed in a secondsubstrate that is stacked with the first substrate via the firstplurality of connectors; and a control unit disposed in the vehicle,wherein the control unit is configured to stop an operation of thevehicle based on a result of the failure detection.